1) Leases can indeed by executed and returned by fax--and, in fact, often are. There is no requirement for in-person signing, hand or mail delivery, etc. If you claim that your signature is forged or the lease was altered after you signed it, that's a different matter--now there's a fraud claim, and fraud can invalidate a lease or other contract. But absent some alleagation of wrong doing, faxed execution or return is legal and enforceable.2) There is no requirement whatsoever that a tenant or prospective tenant has to see an apartment for a lease to be enforceable. There's also no requirement that the tenant ever move in--whether or when you move in is your issue, not the landlord's. It's signing the lease that makes it enforceable and obligates you.