I worked in the retail bike biz as a mechanic, store manager, salesperson for 40 years. During that time my hobby was riding a bicycle. Working on them, selling them and managing a store was my job. I commuted to work year round, rode my bicycle in my spare time, and maintained my personal fleet with pleasure. To this day I love bikes.

It is possible to still enjoy to hobby of riding a bicycle after working on them all day, but to tinker with them as one would a race car after work, it is possible, but difficult to do for fun what you do for work.

To sum it up, if you love to ride bikes, then you can fix and sell them all day and still enjoy riding them, however to fix and sell them after work, unless vintage collectables, that would be difficult to do.