Five years ago, Kat Farmer was a 39-year-old stay-at-home mum. A former head hunter who had swapped city living for country life, she found herself on the cusp of 40 with her youngest child about to start school and suddenly a lot more time on her hands. So she did what a lot of women her age do these days, she started a blog — called Does my Bum Look 40 in This? — then set up an Instagram account. Today she’s a hugely successful one-woman brand with her face on billboards, who has lucrative deals with M&S, House of Fraser and the like, and more than 49,300 Instagram followers to her name. In short, she’s the hottest new trend in social media — a midlife micro-influencer.

“If you’d told me at the beginning how much money I’d be making, I wouldn’t have believed you,” says Farmer, 44, who declines to tell me how much exactly that is. (Bloggers are notoriously secretive about what they get paid.) Farmer started the blog as a hobby and in the past year has seen her Instagram following double. “The whole premise of Does my Bum Look 40 in This? is based around what I want to wear. I wanted to show that just because I was 40, I didn’t have to look ‘classic’ or ‘practical’. Why couldn’t women in their forties look modern?”

Name: Kat Farmer, age: 44, handle: @Doesmybumlook40, followers: 50.2k

Farmer is one of a number of women in their forties who have turned good taste and an engaging personality into a well-paid career as a digital influencer. Erica Davies, 40, is another. A former fashion editor, Davies has 48,900 followers on Instagram, an agent and a salary generated through partnerships with labels such as La Redoute, M&S and Boden. “I started the blog in 2012 after a conversation with a PR who was working a lot with mummy bloggers. I didn’t want to be a mum blogger, but I did want to talk to people like me who had children, but still wanted to know about interiors and fashion,” she explains. Initially writing the blog in tandem with her job at Look magazine, Davies took the plunge into full-time blogging as her following grew and she was approached for projects that she couldn’t do because she was working. “I’ve been a full-time blogger for three years and my salary has gone up by a third each year.”

Not so long ago, to make money through social media you had to be young, hot and have hundreds of thousands, if not millions, of followers. It was an industry populated by models, girls who looked like models and high-profile fashionistas (who probably also looked like models) whose appeal was aspirational and inspirational, but not in the least bit relatable. The next wave of success came with the mummy bloggers and the wellness bloggers, the equally model-y Deliciously Ellas and Madeleine Shaws, who carved out careers sharing their photogenic lifestyles to huge numbers of followers on Instagram. These days it’s also approachable women in their late thirties and forties sharing their style with relatively small followings on social media who have found themselves becoming stars.

I’m a size 12 to 14. People may think, ‘That would look OK on me.’

“It used to be that brands were just focused on how big the numbers were, how many followers someone had,” explains Katharine Richardson, the creative solutions director at WaR, an influencer marketing agency that represents Davies. “Where once you needed more than 200,000 followers to make an impact, that’s becoming less relevant.” A micro-influencer, someone who Richardson classes as having fewer than 50,000 followers on Instagram, is now just as likely to be courted by a brand as someone with hundreds of thousands of followers.

It sounds easy — have phone, take selfie, post picture and Insta-stardom is yours — but it’s not. “Part of the reason why older bloggers are successful is that they work hard and they’re professional,” says Anna Hart of One Roof Social, an influencer media management agency that matches brand campaigns to bloggers. If you think that they’re just a bunch of bored housewives playing around with their phones, then think again. “Creating a successful feed takes a lot of dedication,” confirms Fran Bacon, 42, of @thefashion_lift (39,300 followers). A former buyer for John Lewis who, like many of her contemporaries, began her blog when her children started school, Bacon emphasises how much time goes into what has become her daily occupation. “Even those successful influencers whose feed looks completely natural have spent hours creating that look,” she explains. “I spend hours researching and writing posts, scouring online and on the high street for best buys, meeting with brands to discuss projects, and viewing the latest collections. Time off is rare. Instagram never sleeps, so I need to post consistently to retain readers’ interest. Instagram moves fast and you have to keep up.”

Name: Erica Davies, age: 40, handle: @erica_davies, followers: 49k

“The tipping point came about 18 months ago,” says Hart. “With the poor state of the retail industry in Europe, brands had to do more, but had less budget to do it. Ultimately if you have only got £5,000 to spend on marketing, it can buy very little in terms of traditional advertising. However, you can afford to pay five influencers, each with a highly engaged following of 20,000 people. You can literally have someone on their phone, in their living room, looking at their favourite influencer and learning about your product. It’s a very powerful form of advertising.”

It’s being able to engage with readers that has made influencers such as Farmer, Davies, and Bacon successful. They don’t simply post a picture of themselves wearing something and say, “buy this”, they create a story around that picture, answer followers’ questions (Farmer and Davies receive hundreds of messages a week), engage in conversations and share snippets of their lives with their readers. “The 35-year-old-plus audience is very loyal,” says Richardson. “At that age you tend to follow someone who you genuinely like and who you feel has a similar style. You really do look at what they’re wearing and think, ‘I might go and get that.’ ”

Amanda Start, 47, of @OnlineStylist (17,600 followers) agrees: “If one of my followers has a question and leaves a comment, then they’ll get a response from me, whereas they’re not getting that from someone like Kim Kardashian. It’s like that friend who you go shopping with, but you’re doing it in an online world.”

Erica Davies adds: “I’m a size 12 to 14, I don’t look like a model, so when I wear something people might think, ‘That would look OK on me.’ Women my age tend to have more disposable cash, but less time to spend it. So if they can trust someone whose style they appreciate, who are effectively doing the shopping for them, then that makes a massive difference. It’s like having a virtual personal shopper.”

“It all comes down to that key thing of influence,” Richardson explains. “With a micro-influencer you’re likely to have more of that magic engagement because you have a greater following in terms of loyalty — the people who are following you are particularly invested in who you are. Ultimately if you have an influence over your audience then that is of value to a brand.”

Name: Amanda Start, age: 47, handle: @onlinestylist, followers: 17.6k

Exactly how much that value is seems to vary wildly. Fees can be earned from anything from a one-off blog or Instagram post to campaigns running over six months. There are paid takeovers of a brand’s social media feeds, ambassador partnerships, event hosting and commission earned through affiliate sales. Paid-for collaborations are meant to be declared using the hashtag #spon or #ad, but the issue of gifting and long-term partnerships is less clear. It’s such a murky world that no one really knows what anyone else is being paid, or even what to charge themselves. “I still don’t know what to say when someone asks about a fee,” admits Farmer. “There is no magic number. What I charge a big brand and what I charge a small brand are totally different.”

While some micro-influencers can earn up to £1,000 for a single Instagram post, others may be posting about the same product for nothing. “Rates vary,” says Hart, “as the market is completely unregulated. If you include every type of revenue stream from affiliate marketing to sponsored posts, I’d say that a successful micro-influencer in their forties would be turning over anything from £2,000 to £7,000 a month. As an average fee, we say roughly that it’s £200 per 10,000 followers for an Instagram post, and between £2,000 to £2,500 for a blog post, but it’s very difficult to name a definite price.”

What isn’t difficult to see is why brands love working with micro-influencers who have an engaged, authentic audience. With software easily able to weed out those who have bought followers, comments and likes, the only way to be big on Instagram is to have people actually like you. And when they like, trust and engage with you, it’s more than likely that they’re going to buy through you. “Brands cottoned on to the amount that was being spent through blogs,” says Farmer. “They could see through their analytics where the money was coming from. In the past few years they’ve realised that women my age have money to spend, and in the last year, high street retailers have really got it. They can see that there are women out there who will be influenced. Instagram has been revolutionary in that respect. So many women of my generation shop from Instagram or a blog.”

Davies, who has been known to post a picture of a product and for it to sell out almost instantly, says: “Ultimately it is all about sales. If they can see that your following is engaged and listens to you and buys into what you’re promoting, then that is worth so much to a brand.”

The secrets of Instagram success

Post regularly 
“If you can do it twice a day every day, then that’s brilliant,” says Amanda Start. “Regular posting is important if you want to grow your audience organically. At the time you’ve posted your image, spend 15 minutes leaving meaningful comments on your favourite feeds. This is the way you can continue to build your audience, by upping your appearances in other people’s feeds and interacting.”

Post pictures of yourself
“For a long time I didn’t want to put myself out there,” says Erica Davies. “It was only after friends told me that they liked seeing what I was wearing that I started to share that. I can’t imagine not sharing that now. Interiors and outfits are the two things that get the best response.”

Think about your visuals
“Think if you want your feed to be cohesive and recognisable,” says Start. “Once you’ve decided what you want it to be, play around with editing tools to help to you achieve that. You might find a filter that presents your images in the same way.” However, you don’t always need to be a great photographer to have a popular feed. “My most liked images have been a real mix,” says Fran Bacon, “from changing-room shots of clothes that have just hit the high street to a professional street-style shot. The one theme that ties it all together is that what I’m wearing is available to buy at the time that the photo is published.”

Captions are crucial 
“Long captions, almost mini micro-blogs, have become a huge trend in the past six months,” says Start. “It’s great having beautiful imagery, but I want to have a conversation, so my captions are as important as my pictures.”

Engage, engage, engage
“A huge part of having a successful feed is engaging with followers,” says Start. “I always reply to comments.”

Hashtags
“Make it easy for people to find you by hashtagging your content, ie stick a # sign in front of a tagword,” says Sara Delaney, 52, of @Notesbyastylist (43,900 followers). “It acts like an index, so if you post an image of a white lace blouse, you can bring followers to your feed who are searching for a #whitelaceblouse or a fashion feed. You can use up to 30 hashtags after your caption, but hide them by using five dots on separate lines above them so you don’t look too desperate.”