OK, the least qualified to comment gets 1st go at it ! Brass locomotives are the most detailed models, fabricated with sheet, bar and castings by skilled workers in limited numbers. The types and details can be very prototype-specific in shape, structure and equipment, so each will be a very close representation of a real loco. Because of the material, method of construction, and limited numbers, brass is expensive to build and is made more so by collectors, who treat these as investments to be left untouched, in-original-box, factory paint (or unpainted). The mechanical functions, are "less important", so perhaps less than the best in some cases (the buyer isn't going to RUN them, anyway). If you see a loco that you like, or want because of prototype or because you "like it", and the $$ is reasonable for your priorities - go for it ! All but the worst cases of bad running can be remedied (most will at least require motor/electrical isolation to apply DCC), and a little soldering amnd painting skill will repair/modify most light damage. At worst, you will need to build/buy a display case for your mantel queen. Buying "pre-owned"?- be sure you know what you are getting for your money - if your an E-bay kinda guy, good luck, and watch for those last second run-ups $$$$$$$$$$. I'm sure some others will jump in later with more/better counsel. JM$.02! Bob C. (myusername at gmail.com)