Good luck finding a sub-adult or adult Blood Python for sale, though... I searched the internet high and low before I started buying all of mine a year ago with no luck, because I wanted to speed up the wait time for breeding as much as possible. So, I had to start with hatchlings and juveniles. I found one site in particular (not mentioning any names) that advertised sub-adults and adults for sale, but then refused to sell them after insisting that I fill out some ridiculous "Prospective Owner Application", wanting to know all kinds of personal things that was none of their business on top of other completely unprofessional hassles that whole unfortunate experience entailed...
Anyway... If you haven't ever worked with Blood Pythons before it's not a bad idea to start with a hatchling or juvenile. That would be my recommendation, actually... Even though, most of them tame down pretty well, their general demeanor is much more intimidating than any other species i've worked with. The last thing you want to do is show these guys any fear or let them think you are intimidated. They can put on quite a show until trust has been established! lol One of my Borneos started out sweet as can be for the first month or so then just completely changed overnight a couple of months ago and is still acting schizo. With all but two of my other ones, it was the exact opposite. They acted schizo for for about the first month or so, but have been puppy dog tame ever since with the exception of a couple isolated incidents. If you start out with a hatchling or juvenile you can grow and build trust together. Fortunately, I haven't ever been bitten yet, but I think it's pretty safe to say that a larger Blood Python could do a lot of damage. Just some things for you to consider...