A 5 year old boa is about as big as he's going to get. 6ft is a decent size for a male BCI. He will need a large enclosure though. 4x2x2 or similar as a bare minimum. And despite what many say, boas will climb if given the opportunity. Bigger is always better with boas.

Boas are generally pretty laid back. If you are going to the home of his owner to see him and handle him, you'll get a good feel for his personality. He should be curious and boas are usually pretty active so expect him to move a lot and climb all over you. But if you can get him out of his cage with no trouble, and there's no hissing or puffing, he's probably gonna be fairly tame. Don't worry if he's a pain in the butt to put BACK IN his cage though - boas hate to go back!

Quarantine is a vital must with boas, and be very strict with it. 60 day minimum and 90 is better. Boas can carry IBD (which although more rare than originally thought to be, is still a very real threat) and this is almost immediately fatal to pythons. Keep your eye out for any neurological signs. I would also treat the snake for mites whether you see any or not. Use this from Reptile Basics. It is by far the best product on the market - yes, even better than PAM - since it's safe to spray directly on the snake. I just give a quick spray down of any new arrivals and prevent mites right from the start.

Boas are usually garbage disposals and will readily take f/t. Did you say f/t rats in your area were $10-30 a piece?!? If so, order online!! Even with shipping, you'll save a bundle! I get mine from www.laynelabs.com and I've been very happy with them. Excellent quality. And you can order in small numbers if that suits you better.

Hope this is helpful!