Rescued a Boa, need some help.

[Cmwells90]

So last night I saw this sales post on FB for a guy selling a Hypo male Boa. I was totally into this idea cause I wanna use one if my breeding project and he's an adult so it's perfect.

However I picked him up late last night, he's about as long as my 3 yr old female BCI, 5.5 ft ish. But he is REALLY skinny, like corn snake size. He clearly hasn't been taken care of properly (big surprise). Well I've never really taken in an unhealthy animal, but I want to try to nurse him back to a good health. He's incredibly lathargic, which I would assume would be from improper feeding. I can handle the stuck shed and hygine of the cage, but I wanna make sure I bulk him back up properly. I've heard that you don't want to rush them straight to full sized prey items, is this true? Start small and work it up and he bulks up? I know he's not going to be ready to breed this year, but if I can get him back to health, do you think it'll negativly effect his breeding abilities? I'll have more questions later I'm sure, and I'll post picks when I get it all started and cleaned XD.

Thanks!!