The first thing to do is to see if a market exists. Place some ads, answer some emails with details about your fees and see how it goes . Just about every aspect of bike sales is low profit. I think human nature will cause people to do what they do now. Buy the cheapest thing possible, and then learn after the purchase, they made a mistake.
I hope I'm wrong, try it. As mentioned, some on line ads, or in the paper is not a big loss, it they don't work.