I found a car that I wanted, so I went to check it out. I don't have enough cash, I could definitely do a down-payment with monthly, but they said that they only accept cash and that I had to wait for the owner. I asked around and apparently the cars in the lot are from a bunch of private owners who grouped together to form the dealership, using the dealership as a ad essentially. Are these kinds of dealerships ok to buy from or is there something else I don't know about?
That's called a consignment lot and yes, they are perfectly ok to buy from. The cars are owned by private sellers who pay the lot either a set fee or a percentage of the sale in return for parking their cars there. This benefits the seller by providing a safe environment for them to sell, plus giving their vehicle better visibility to the public.
These are common and are not a scam. Just be sure you have the vehicle checked out in the same way you would if buying privately at someone's home and you'll be fine.