Your bread and butter will come from repairs. Probably from really crap low end bikes. The dream and reality are often very different.
Just because you don’t sell road bike, doesn’t mean you cant sell spares and repair them.
As stated before be prepared for robo shopping! (Research off line, buy online)
Do you think you can compete with online sellers discounts?
My friend runs a shop and he says its more a lifestyle choice than making money. He also says the famous bike industry joke is if you want to make a million out of bikes, start with 2!
Having said that, cycling is the in thing at the moment and due to petrol and parking commuting is very popular. Personally, I would try and tap into that market, r2w scheme, local businesses etc
Good luck.