Four wheels to a fortune

It's a book about buying and trading cars, usually bought for low prices at a trade auction, refurbished nd then sold for a profit.
It sas sold by classified advertising in places likevthe Exchange and Mart. It made a massive amount of money for Charles Cust before he got into selling a scheme called "the Key to Success & Wealth" which was basically a scheme similar to pyramid selling produced by a company called Paper Moon Publishing.