Everybody who works in a bike shop knows what the pay is going to be before they start. It's relatively easy to figure out if that's going to be enough to meet your needs.
Working conditions can be a bit murkier.
Most people who take bike shop jobs do so because they are into bicycling. Most bike oriented events, races and the like, are held on weekends. Guess what the biggest sale days are for bike shops?
I once worked for a bike shop that wouldn't let me take a weekend day off - EVER. So here I am, working full time in a bike store, and I can't participate any bicycling events (not to mention things like family get-togethers). I hated it.
Trying to schedule a vacation wasn't any easier. A guy who I worked with tried to schedule a week's vacation during February, our slowest month. Well, February may be slow, but we maintained a minimal staff during February too. He eventually got authorized to take the time off but not until after he had lost the opportunity for lower cost travel tickets.
Speaking of which, are you talking about a 12 month job or a May to October job? Don't assume that you're being offered a 12 month job unless they actually say it.
Incidentally, I'm a school bus driver today. A year and a half ago I talked to the owner of a local bike shop and offered to trade wrenching for bike parts. Today I work maybe 4 hrs per week through the slow months and a few more hours during the busy months. The hours that I work fit in with my school bus schedule and it's just enough to keep me from feeling stale.