All I've ascertained is that the ATF requires a "Class 6" permit which is a trivial cost. Does anyone know what caveats a Class-6 requires?
I read a passing comment on a different forum about requiring a store front. This would be the perfect motivation for both selling my sailboat for investment capital *and* open a gunsmith operation.

However I don't know the details, and I know someone who operates a similar business out of their garage, so the storefront may not be necessary?