I also have a farm, after years of using stick I finally changed over completely to tig, mostly because of the fire and damage risk. Tig's slower and I have to clean everything better first, but I don't have to worry about burning down the barn or starting a field on fire. I also sent a hot spark across the room and onto the cylinder of my tractor, which left a nice pit in the surface that caused a leak. I end up welding a lot of thin material, like gate panels, hinges on gates. It's pretty hard to do that kind of thing with stick, even if you're really good. If I need to weld in the field, I roll the cart into the bucket of the tractor and hook the generator on the back, it's nice to have an inverter machine that weighs 50# rather than a transformer that weighs 200.
You can probably get a used inverter tig machine for your budget of $600, I just saw a used AHP with tank and cart for about that amount of money on craigslist. If you go stick, I'd echo other comments and look for a used Lincoln 225 tombstone, they're indestructible.
