curber
n.— «Unlicensed motor vehicle dealers are commonly referred to as “curbers,” usually operating from their homes, and collectively represent hundreds of millions of dollars in vehicle sales each year. The public has no protection from these individuals.» —“Self-proclaimed ’hobbyist’ convicted as illegal car dealer” in Burnaby, British Columbia CNW Group June 19, 2007. (source: Double-Tongued Dictionary)
This is related to curbstoning.