Note that age of the bike and component fanciness (e.g. trigger shifters vs. friction lever shifters, or 10-speed cassette vs. 7-speed cassette) is mostly irrelevant as long as the old or lower-end stuff is in good working order. My commuter bike (a 1990-ish Specialized Hard Rock) has an '80s-fad
ovoid crankset and "ankle-biter" wide-profile cantilever brakes, and that's just fine.
Pay close attention to the frame, though: an old cro-moly frame is generally better than a new hi-tensile (or unlabeled "steel") frame, as long as it's not damaged or excessively rusted. (Surface rust is okay, just poke it with something pointy to make sure it's not rusted
through. And then paint it so it doesn't continue to rust.)