The boa will get to be 7 feet if it's a MALE redtail. Females will get anywhere from 10 (average) to 12 (large) to 15 (astronomically unlikely, but it has been recorded before.)
If he tries to feed his snakes every 2 days, he will kill them. Powerfeeding is NOT good practice. Sounds like this jackass has some sort of stupid dream in his head that he can powerfeed and grow these snakes up to sell them for a profit. Well, as mentioned above, zoos won't take burms or boas for FREE, much less for a fee. They are already overstocked with them. Tell this jackass he has no right to be keeping reptiles, but do let us know when he will have them up for adoption, because he WILL.
- Ken LePage