Never owned a shop, but was a mechanic in 2 over 6 years, one in Sydney and one in regional NSW.
It's a tough gig. If you know how to manage customer expectations and are a good communicator, that will help you a lot. You can do the best job 99% of the time, but 1 grumpy customer can undo a lot of good will.
You probably won't be selling a tricked out Santa Cruz every day. If you're not stoked at the idea of most of your sales being kids bikes and commuters for inexperienced riders, you may need to adjust your expectations.
Working in a good shop is fun, but, IMHO, if you're not careful, mixing work and play can really affect your love of bikes. You will be exposed to the money grubbing side of the industry and bullshit marketing, day in, day out, suppliers can try and strong arm you into stocking more than you want to, or fitting out your shop differently.
Having said that, I've been out of the industry for 4 years, but regularly find myself thinking about spinning some spanners on the side. There is something wholesome about bikes and working with them. Just protect yourself against all the bullshit and defend the reasons you go into it in the first place.