In hindsight, Jim Snyder knows he should have had a mechanic check out the 2003 Chevy Cavalier before he bought it. He didn't, and the oversight cost him $500. "Under no condition would I buy a used car again unless a mechanic sees it first," says Snyder, of Carmel, Ind.

Used car prices, traditionally more stable during economic downturns, are slumping as dealers resort to deeper discounts on new vehicles. For example, in November the cost for a typical used 2004 vehicle dropped 5 percent compared with the same period last year, says Joe Spinna, senior marketing manager at auto industry analyst Edmunds.com. "It's definitely a buyer's market out there," Spinna says.

But a deal is only as good as the car. "Watch what you're signing and remember that oral promises are almost impossible to enforce," says Harry Bradley, a Chicago-based consumer protection lawyer and former mechanic who practices in Indiana. "When you buy a vehicle 'as is,' you buy it with all the faults and defects. The law's not going to protect you."

Snyder helped his son buy the Cavalier from Andy Mohr Buick Pontiac GMC in Fishers, Ind.. Shortly after the sale, Snyder's mechanic found $500 in brake repairs. Bob Siderys, used car manager at Andy Mohr Buick, says although he can't comment specifically about Snyder's claims, the dealership's used vehicles pass its own inspection.

Jon Hubner of highly rated Hubner Inc., a Lafayette, Ind., used auto dealer available on the Internet in Indianapolis, says consumers need to do their homework. "Most people don't qualify the car they're buying with an independent mechanical inspection," he says.

Vehicle inspection prices vary by the mechanic, but customers can generally expect to pay under $100. "For a visual inspection, we charge $38.50," says Jim Trump of highly rated Castleton Auto Repair in Indianapolis. "If that shows a red flag, customers can opt for a more comprehensive inspection for $75."

Sue Schnepf, of Indianapolis, also says a mechanic's inspection could have helped her avoid a headache. She bought a 2006 Lexus GS300 in 'as is' condition from Coast to Coast Imports in Fishers. When a low tire pressure indicator came on three months later, she discovered standard-equipment sensors were missing.

Buyers of newer vehicles have more options when it comes to mechanical problems. Indiana's Lemon Law protects consumers under certain conditions. Problems must be reported within 18 months of when the car was originally sold as new purchase or 18,000 total miles on the odometer, whichever comes first, and the vehicle must have been bought from an Indiana dealership for personal use. (For more information, go to the state attorney general's website, indianaconsumer.com.) The law also allows an authorized dealer or manufacturer to make reasonable attempts — at least four failed repairs or keeping the vehicle unavailable for a cumulative total of 30 days — to fix the issue.