I am looking at getting a tig and learning to make stuff

I'm skilled on a MIG welder but have not used tig.
When buying a tig, what am I looking for?
What types can I get away with?
I want to weld intercooler piping, upto 3mm plate and
brackets.
What am I looking for? Brand, amp, style and price?
Anything available around $1000-1200, or lower?
Second hand or new?
Cheers