Equally you could find that the most popular bikes are a well established market for existing bike stores in your area or for online purchase.

You may of course be starting in an area without existing provision, but if you are then you'll need to compete with the existing shops: service and price obviously count, but so too might targeting more niche products.

Many ways to skin a cat.

ETA: Reminds me of the old joke: how do you end up with a million bucks from running a bike shop? Start with 2 million.