I have to disagree with the mechanic. Many, many vehicles have timing belts, and run forever, as long as you fork over the $500 or so to replace the belt every 90,000 miles or 7 years, whichever comes first. It's really not an inconvenience. There are many quality vehicles you'll overlook that have timing belts if you hold to that reasoning.
For example, my 1999 Accord has a timing belt, and I surmise that most if not all Honda/Acura 4-cyls have timing belts. For a vehicle that sells well over 300,000 copies a year, the timing belt is hardly an issue. OTOH, 6-cyl models of the same behicle may have timing chains, but no one cares. They're all different between make and model, and I would not advise you to even consider whether or not the vehicle you are buying has a belt or chain, unless of course it has 90,000 miles on it and needs a replacement, in which case get $500 knocked off the asking price and arrange to get it replaced if you buy it.