I've been working in the 'outdoors' since 2006 and running my own company since 2009. It's great fun, the best office in the world - and hard work.
I started off (and still do occasionally) working for other people. I gained my Summer ML in spring 2006 and led charity groups doing the National 3 Peaks all summer - 18 times! Other work with D of E groups, days guided walking here and there and working with school groups took up the next 12 months, with bits and pieces of work elsewhere. I gradually built up the experience, contacts and hopefully reputation to branch out on my own a few years later. I gained more qualifications, tried to go on as many trips into the middle of nowhere in 'interesting' and kept practicing my skills. Most of my work was in the mountains but I developed skills elsewhere, following my interests.
Once I set up on my own I offered a range of courses, from mountain nav to foraging and bushcraft. Linking up with other local businesses helped as we could cross-promote. I built my own website and learnt how to use social media to my advantage, and tried to stay cheerful in the face of high costs and low pay - the same as any other small business I suppose.
Now my business is comfortably supporting me - but bushcraft is only a part of it. As others have said it is wise to diversify, and I love the fact that I get to work on the mountains, in the forests, sometimes in urban areas doing unusual things that I am interested in. On Wednesday I will spend all day foraging on a 70,000 acre private estate near Corwen for their wholesale gourmet food business, and spending the rest of the week updating the website, carrying on with building new tipis and shelters at the school site and getting teaching materials ready for this weekend's course.
Working in the outdoors is tough, and few make a good living from it. If you have your ML, SPA and a third 'ticket' such as BCU or mountain biking and are willing to live out of the back of a van occasionally then you could work as a freelance instructor earning about £15k per annum. If you go for a 'steady' job working in a centre or elsewhere (an increasingly rare option these days though) you might be able to push that up to £20-£25k. That's all pre tax and costs etc. I would strongly recommend anybody going into teaching outdoor/wilderness skills getting an NGB award such as the Summer ML. Military experience is good, something semi-transferable such as the JSMEL would be even better - but convincing your insurers that you are competent to lead a civilian group in a hazardous environment could be tough. The Summer ML has few links to what we would call bushcraft, but it does cover navigation, group leadership, wild camping and other related stuff in depth. There is no industry-standard 'Bushcraft' qualification at the moment, although courses do exist.
The above sounds a bit negative - it isn't intended to be, I love my job and couldn't sit in an office all day. It's just a conversation I have regularly with people so I'm used to trying to give a balanced view on the practicalities of it.
I'll happily have a chat on the phone if you wish, PM me etc.