Amen to the business about learning to run a business. That is excellent advice, but permit me to add two points.
First, carry insurance, and plenty of it. If you have a fire or other disaster and lose your stock plus customer guns you will be bankrupt. Also you might need coverage if you are sued because you did something, even if it was legal, that someone thinks was wrong. (Example: You sold a gun to a campus killer; he passed the NICS check, but a victim's family says you should have known he was a nutcase.)
Second, don't operate out of your home, even where it would be legal to do so. Gun shops are magnets for burglars and you don't want your family endangered by druggies looking for guns. And you don't want to be wakened in the middle of the night by some nut who wants a gun to go hunting that morning.
Also, FWIW, I advise against a web site, unless you plan to do all your business that way. You can't be "on line" and at work at the same time. Plus, you don't want to get tangled up in endless e-mail exchanges with people who just want to show off their expertise or who want to spend hours telling you how cheap they can buy somewhere else.
As to transfers, it is your decision, but I see no reason a dealer should do a transfer on a gun when he has the same gun in stock or can order it. That is dumb and IMHO, the dealer should tell the "customer" to take his "business" elsewhere. Now, rare guns, or collector guns are another story, and most dealers will be happy to do transfers on those.
Jim