He'll need to find a Registered Reciever for sale, or DIAS or LL, RR are selling for around 14-17k right now, RDIAS are like 12-14k, LLs around 10-12k. Once he finds something he wants, he'll have to get an ATF Form 4, fill it out, then get it signed by his local Chief LEO, or form a Corperation. Then send it and a 200 dollar check to the ATF who will take their sweet time to aprove it, then eventually send it back with a aproved tax stamp attached too it, then he can give money to the person who he's buying it from. All of this is dependant on the fact he lives in a NFA state. If he finds a RR thats out of state, he'll need to find a dealer who can transfer it into the his state of residence, this will take an additional form 4 and another 200 bucks. Once he gets this all done he can take home his new toy.
ETA: check the NFA side of this board, lots of good info there.