There are too many considerations for a post here, but the number one consideration is location, and whether the surrounding population is adequate to produce an adequate customer base. If you talk to owners of struggling stores, the common theme is "lack of traffic". It doesn't matter how good you are, how well merchandised the shop is, or any other positive, if there simply isn't enough base to make a go of it.

The next biggest factor is rent and utility costs, as compared to sales. In most of the USA the bike biz is highly seasonal, so a good part of the year, you'll be shelling out dough to keep the door open, with few people coming through it. The rest of the year you might have more traffic than you can support.

Before you commit, work up a reasonable estimate for the potential gross volume, then subtract the cost of doing business (aka the nut) from 40-45% of the gross volume, and that's what you have left for some payroll, things like insurance, incidental expenses, and (oh yeah) yourself.