That was what I had in mind. My son runs a cycle service, build and repair business and without ever advertising, makes as much in a four day week as he did as a secondary school teacher. He taught science and was on a good salary. If he took on every job that he was asked to do, he'd be working 7 days a week. He's very good and meticulous. That certainly gets business.
It doesn't matter which cycling themed cafe, plus workshop and components outlet we go to, they're busy, especially at weekends for the cafe and week days for spannering. Components mark up is crazy.
Just need a good mechanic, not a huge investment in workshop tools and parts (we helped set our son up and it wasn't a huge amount) and away you go. Add a small seating area, couple of TV, coffee and locally sourced cakes and savoury options and you should be able to make a reasonable business in a fairly short time.