Are You Buying a Used Car from a Private Seller? Or a Curbsider? August 16, 2019October 3, 2019 Posted in Car Buying Tips. If you’re in the market for a used car and respond to a classified ad from a private seller, make sure they’re not a curbsider. Curbsiders are people who pose as private sellers, but are actually running a business selling cars. ... Read More.