Companies such as Redbull, Rockstar and Monster have paid people to place advertisements on their personal vehicles. The companies offer pay between $200 and $500 monthly to rent the ad space. There's also a "free car" system; the company provides a car to a person to drive without cash payment.
According to the Better Business Bureau, there are not many legitimate companies paying for this type of advertisement. Scam artist often use the names of popular companies to make the offer seem valid. If a company asks for payment of any kind it should be seen as a warning sign.