Setting up a business involves the same process, regardless of what it is. How big is the market? where is that market and how do reach them? what prices will that market stomach? Does that leave a decent profit margin? What competition is out there? How are they doing? what is your value proposition compared to theirs? etc. etc…
Try and keep your passion for bikes out of it while you answer those questions objectively. Unless you just want to do it for pin money in which case give it a go.
Personally I do it for beers/favours, and have a deal with my “customers” they must have rockshox/shimano equipped mtb’s to make it easy for me :D