Mr. Dirt didn’t invent the practice of renting a race car; he just made it fashionable.
For obvious reasons, Mr. Dirt prefers to keep his true identity unlisted, but it can be revealed with a reasonable amount of detective work. He prefers to have a race car he doesn’t have to do anything to but put in gas, and even then, with the option to return it on empty – he can just run off of a pre-paid amount. He simply rents them and returns them after he’d picked up a fair amount of loot in the process.