I opened a shop about two years ago, it's been great. After a short while, I offered a colleague a share of the business so that we could operate as business partners, and that made things better in every way.
You will need money, and quite a bit of it, to open a bike shop. And even after you open, a line of credit with a bank is pretty much a necessity. And keep in mind, banks don't lend money as readily as they did two years ago (this is one thing that's been an eye opener for me, as I've had a very good relationship with my bank for decades, but now they're not nearly as easy to work with as they were). A business plan is essential. The willingness to work LONG hours is essential. The willingness and ability to work retail is essential, because the reality is, that's what you're doing in selling new bicycles.
If you REALLY want to open a bike shop, you will indeed need a brick and mortar location. Companies like QBP and bike manufacturers aren't going to deal with you if you don't have a retail location. Choosing bike brands that you feel confident in and that are available in your area can be difficult if there are established shops in your area that already carry the mainstream brands that you would like to carry. This took some thought and deliberation on my part, and while I'm happy with where we are right now, it is a dynamic process (things change, sometimes rapidly, in local markets).
I contemplated starting some type of bike business for quite a few years before I opened our shop, I even incorporated the name three years before the shop opened. But I never REALLY made the commitment to do it until the very end of 2007/early 2008. Once I made the commitment, I mean REALLY made the commitment, things happened pretty fast. Again, getting a location, then establishing yourself with suppliers and manufacturers, is a big deal and you're only going to do these things if you're REALLY committed to your idea.
From a mechanic's perspective, you will learn more about working on bikes in a bike shop environment in a few months than you can learn in decades of working on your own bikes. But keep in mind, if working on bikes is your passion (it certainly is one of mine), there's a lot more to running a bike shop than working on bikes. The bookkeeping alone is a huge responsibility. In addition to the two partners, we have two others who work here (think payroll). It's cool, because we're all truly bike nuts, but again, there's a lot of responsibility outside the realm of bikes.
I do have the advantage of having been in a couple of other businesses in my life, so most of the business side of things is not new to me (although business is a dynamic process, and every business is different). A major highlight of my time in the bike business so far was a trip to Interbike in September. My business partner and I went together, and it was heaven on earth for a couple of bike nuts. We hope to continue to go there at least every few years. Enjoyable as it is, it really is good for your business to get out there, meet people in the industry, and check out new stuff.
Good luck-