Liz, just make sure you get it checked out before you buy. I had mine checked by SGIO. RAC wanted $250 for a check, SGIO only wanted $120.
What I want to know is, why does it matter what the purchase price of the vehical is anyway for an autocheck? Will they do a better check if you are buying a $50 000 BMW than if you were purchasing a $500 Datsun?
Anyway, a check is well worth it, it will give you an idea of what maintenence is upcomming, how worn the breaks are, electrical systems...they are very thorough.