I don't own my own bike shop, but like you have worked as a mechanic for them for a long time. when I’m in Florida for school, I work at a small shop, co-owned by two guys who own that one and another small one up the road about 5 miles. One does the high end road and mountain ($3000 to about $15000), and the other store does the more entry level stuff and beach bikes, since we're across the street from the beach. I have been working for them for 3 years, and learned a ton about owning and operating a bike shop from them.
I’ll start out by saying that both of them have other jobs. As you know, markup on bikes is extremely low compared to other forms of retail (like clothing). So make sure you put lots of thought into the lines of accessories you will carry, since that's more than likely where the biggest chunk of your profits will come from. The other thing I have learned from them is that labor will make or break you. If you have 3 mechanics in at a given time working for you and there is only one bike being worked on, even if it only takes 2 hours to fix and the bill is $200, you still have to pay 3 people for their time. Depending on their skill level, and therefore, their wage, that could just about kill the money you just brought in. On the other hand, if there is a steady flow of labor and it is being properly completed in a timely manner, you can potentially make more from labor than parts and accessories.
Brand selection is also important. First you have to choose what brands you want to carry. Giant makes great bikes, but they have a habit of getting dropped from stores because they require you to stock your store with too high or a percentage of their stuff. you also don't want to carry the same brand as the bike shop down the road unless you are positive you can make sales over them, either based on customer service (which you haven't built the reputation for yet), or price (which is how you might have to start)
The other potential killer is overhead. There are costs to keep the business running that you never think of.
Bottom line is that you will need more money to start up than you think, so get your loans a little high if anything, and you will have to invest more time at the beginning than you think.
I would look for an assistant manager to hire that understands what's going on, and is ok with putting in long hours for slightly less pay at the beginning, knowing that when things are settled in and pick up, you will appropriately take care of him for the work he's put in (or her). Weather that's a bonus, back pay, or whatever, it will help greatly to have someone to split the start-up work with.
I apologize that I haven't really actually given you much advice, but more just stuff to look out for and expect, but I hope it helps in some form or another.
Best of luck in your new business endeavor! There are far too few independently owned and operated bike shops. It’s good to see someone doing what they love and changing that.
I’m very interested in where you take this, so I’ll follow the thread and let you know if I think of anything helpful.