It has been awhile for me, about 5 years, since I was in the car business but here is what I remember.
Dealership license is tough and requires a good investment. As thesanchez said, at least here in PA, you need to be bonded, have dealer insurance and a stable business location that can hold cars. You need to go through a huge package of requirements, including taking pictures of your business, posted hours, handicap spot sign, lighting, doorway measurements and so on. Basically, they are trying to cut out the shady shit.
However, a wholesaler license is different, which is the bare min you need for any good auction. I am not sure what all is needed for that because I ran dealerships, not wholesale businesses. But, with a wholesale license, I am not sure how many cars you can sell to the public without having to get a dealer license. But there is a large business in wholesaling directly to dealerships. Cuts down on their expenses if they outsource that, so you could always do that until you have enough to get your own lot.
In PA, your lot can be small, but I think it has to hold something like 5 cars on it and you have to be able to open your front door of the business when those 5 cars are parked there. That is directly from the requirements actually lol So, you don't need a lot, but you will need to drop some money on the bonds and insurance. Hope that helps you out a bit!