I assume you're like minded with your budget of 3-4k but I'll add that going cheap on any thing related to metal working is a huge mistake.
Welders whether mig, tig, or stick.
Plasma cutters, milling machine, lathe whatever.
Once in a while a friend or aquaintence will say "hey I got this xxx, can you get me going on it"
Some sort of cheap home owner/hobby things and the limitations present themselves immediately.
If budget was lower I'd recommend the most expensive fairly priced used item in that budget.
Same as gun stuff. "Buy once...."