Well, this is true for FFL 01. But not for an FFL 03.
There are actually several different Federal Firearms Licenses. 01 is the common dealer license. 03 is for collectors of curio and relic firearms. There are no business requirements (in fact intentional profits are a no-no) and the cost is lower ($10/year).
Agreed, but the context of the OP's question implied an FFL01 (i.e. do you need a building, can you use it to make extra money, etc.)