To legally purchase a suppressor/silencer or any item falling under the purview of the NFA, you must be at least 21 years of age, a resident of the United States, and have no felony record. And pay all the fees and wait and wait and....
I'm kind of curious about that as well, I kind of want to start paperwork on mine soon so I won't have to wait a year to pick up my birthday present to myself.
Must be 21 to start paperwork. You buy from another individual in your state on a Form 4 when you're 18, or you can Form 1 and make your own. Must be 21 to buy from dealer.