The rule of thumb is you need a 220v for frame work(10 gage & thicker) but, 115 will sufice for body work up to 14 gage.If you can not afford a 220v MIG, I would but a stick welder.
I use a 250 amp TIG or a 200 amp MIG for my frame work but, a 160 amp would work fine.

My welders are Miller because they are real reliable & they were what I was certified on however, Lincoln &Hobard area also good. Hobard is probably the cheapest. They have a 185 amp that is available. Look on-lne for the cheapest prices.