I agree with the above posts, Burms are NOT a good beginner snake, despite their great personalities and easy to handle natures.
I have a burm, named Bandula. He is currently 3 years old, 14 feet in length and weighs almost as much as I do (120lbs.) Your friend is in need of a wake-up call unless he really knows what he's getting into. He's already been bitten once, in the future (with a larger snake), that bite can turn into coils and death.
You didn't mention how large his snakes are, but in any case they grow like weeds anyways. I think the record for Burm's is something like 27 feet and 420-something lbs. (This is the famous 'Baby' that recently passed away at 15+ yrs. in age).
Many pet burms are given away, set free or euthanized once they reach 10 feet or so. This is a major problem with the species, and anyone owning one should commit to it for it's entire life, and do all the right things to keep it (and us) safe. Most, if not all, states require special permits for the keeping of large constrictors. If you friend gets caught keeping them illegally the snakes will probably be conficated and euthanized. So not fair to these beautiful creatures. If he seriously wants to keep them, direct him to this site and we'll help him do it the 'right' way. Please update soon!