Joc:
C&L/SA/SAO: Cocked & Locked/single action similar to the 1911.
DA: Double action, where the hammer is cocked and then released to fall on the firing pin.
TDA: Traditional Double Action, where the first shot is a long & nasty double action and the subsequent shots are a sloppy single action. Usually has a manual safety that can be engaged that may or may not decock the hammer if in SA mode.
Decocker: Doule action with a decocker but no manual safety.
DAO: Double Action Only, usually no manual safety
In general, double action semis have gawdawful double action triggers and creepy & sloppy single action triggers. DAO is the least obnoxious of the bunch and TDA the most obnoxious, IMO. Some of the individual models are high quality weapons, though.
IMO, DA autos were a hardware solution for a software problem.
If you can tolerate a double action, the S&W semis are some of the best quality ever made, especially the third gen. Cheap used and lots of mags out there for them. They came in TDA, DAO, decocker and 9mm, 10mm, .40S&W, .45ACP in all-steel or alloy frames in full-sized, compact & sub-compact. The whole gamut. If I were on the hunt for a cheaper (price-wise) 9mm DA semi, a used S&W third gen is where I would start.
If I were doing the same for a C&L-capable 9mm, the CZ75 & BHO are the obvious first options.
Good luck.
If you can stomach a DAO in .40S&W, this will answer the mail for $280 bones:
http://www.summitgunbroker.com/4043.htmlExtra mags $10 with purchase.
Excuse me while I send this link to my dad, too....