Purchasing a car from a private seller. Nightmare.

In regards to the title, here in Wisconsin I am told that you can purchase a "wholesaler's" or "dealers" license or permit from DMV. This allows one to buy and sale up to six? vehicles per month, without paying sales tax and without having to get a new title. There is a separate document (bill of sale or receipt or something similar) that documents the transaction, but the wholesaler or dealer doesn't have to register the car in his/her name or get a new title. When purchasing a vehicle from a wholesaler or a small independent dealer, the previous owners name will appear on the title. Is my understanding of this correct, or have I been given incorrect information? Most importantly, I suppose not having to pay registration fees and sales tax (5.5%) is the reason flippers and small, independent dealers go this route.