When I started brewing 4 years ago, I bought a cheap Proctor-Silex 30 qt. SS pot from Cooking.com, $40 shipped on sale, to go along with my Midwest brewing kit. I'm still using it. It's got thin metal, and has some dings around the bottom edge by now, but.....it works. For me, this is about the minimum size pot to do full 6.5 gal. AG boils. With that much liquid in there, it comes to within about 2 inches of the top. Boilovers would be a problem except for a handy product called Fermcap-S. Six drops at the start of the boil, and no worries. I have no plans to upgrade to a bigger pot......that would only happen if I would make the jump to 10 gallon batches, and I don't see that happening.
“Malt does more than Milton can / To justify God’s ways to man”
-A. E. Housman (1859–1936). A Shropshire Lad , 1896.