I'd say to get a Columbian boa. Males normally stay smaller, say 6 to 7 feet. You could get a nice hypo or pastel for under $300.
I think you'd be surprized at how nice they are to handle.
A male could be kept in a cage as small as 2'Dx3'Lx1'H. I keep my male in a cage that is 2'Dx4'Lx2'H. They like to climb and bask under a light bulb. Of course a young boa doesn't need that big of an enclosure. But, they grow fast, so be prepared for the need of a bigger living requirement.
As always, do your research! Let us know what you decide.