Some feedback for you dude... I made the leap, around June/July last year.... previously on a well-paid/high pressure job that had seen me grow a decent wedge to be able to stick my neck out and take a few chances in life and get myself into a better head space.
I'm a qualified mechanical engineer but actually haven't used any of that quali for my last 17 years of working life haha... in terms of cycle mechanics i've gained experience over the last 20 years with friends/family/locals and my own fleet - building/collecting bikes was at one time my very expensive hobby!
So I started from home, in a large, very secure workshop but work purely mobile - in that nobody visits me at all - this aids with lowering both house and business insurances, better security and I have complete control over my working days in that unlike a shop I don't suddenly get a bus load of customers come through the door at once. I conduct the repair mobile if i'm able, if not able to do it mobile or for servicing then it comes back to the workshop and then gets delivered back completed. I COULD NOT have timed it better in fairness, right at the cusp of the massive cycle boom, got on the governent voucher scheme which saw me take HUNDREDS of these as the local shops were refusing to accept them for all manner of reasons. I'd say Oct 2020 to Oct 2021 i could not have been busier, I've done roughly 1000 services in that time, it has now slid off quite dramatically. Mixture of time of year/weather/xmas/inflation but i'm not panicking as I know i've certainly made hay when the sun was shining & that it will come back, tbh also slightly grateful it calmed as no way could I carry on at the rate I was - I'd have burt out!
You HAVE to be in the right area, be business minded and determined. I've managed to get lucky on quite a bit of decent stock from failed/closing businesses and know your market well to buy in when the price is right, you'll be amazed at how much the market fluctuates. It is hard graft, I've given myself the worst tendonitus in my left hand/wrist which won't go away and hoping to get it scanned at hospital to see exactly whats going on in there, but im struggling on - it's usually freed up after the first hour or 2 haha.
I'd say my love for bikes has changed somewhat, there were times earlier this year where I haven't wanted to see another bike but i'm over that. Also don't be afraid to say no/turn them away if it doesn't suit - i've had some serious wrecks in that have taken me hours upon hours to sort out. Know what types of job earn you the most & always have these in the forefront of your mind, for this reason i've largely stopped any wheel building as I can earn twice as much servicing in the time.
Not sure if you've been self employed before, I've been self employed since 21-ish and im now nearly 40, my previous job held huge responsibility, if I messed up I'd receive a whopping fine &/or possible criminal record. The next year will certainly be an interesting one, I'm NOT anticipating it to be anywhere near as good as the last 12 months, hell we've just had the biggest cycling boom of our lifetimes I'd say! Main factor being everyone back to work with less time to ride, less disposible income to splash on luxuries and passtimes due to inflation rising and if interest rates also increase as they are due to, this will also have a factor. Luckily I've tapped into quite a few road clubs, these are firm regular customers and loyal, i'm also big with the parents/school parent community who's teenage kids demolish bikes/get flats weekly and they tend to keep me busy too.
Final note - if you've got big mortgage/family to support/stuff on finance etc then there is obviously an inheret risk and it's a whopping decision, however if like me you've got fairly low overheads/commitments then taking risks, well, isn't so risky.