Lots of great old lathes out there. As others said stay away from bench mounted. Also pay particular attention to spindle bore. Monarch & Hardinge made the cadilac of manual lathes. Both tend to be a small bore. 1-1/8 to 1-3/8. You can usually get your best deal on larger swing and longer bed models because less back yard type guys want them. I have a 17x96 Cinncinatti that I paid $1500 (plus rigging) its in A+ condition. I also have a 13x36 Colchester that I paid $15k in similar condition.
Colchester, Sheldon, LeBlonde all make good quality smaller lathes that you can get for $5-$8k on the used market in good condition. Bought a HF lathe for my kid as a training/toy. It will only cut about .015 (diameter) in steel.
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