Fun question, but it leads to other questions...

First, are vampires stopped at the property line, or only at the threshold of some appurtenance (e.g., a house)? After all, you're asking about real estate, and real estate is primarily concerned with land, not buildings.

This sort of matters because, are we assuming that vampire law is coincident with human law? By this I mean, if vampires were to take control of the government and abolish real estate law, would they then be able to enter any property or building, anywhere, anytime?

If vampires do observe human law, then realistically, they probably wouldn't be able to enter a leasehold without the tenant's permission. The fundamental right of tenancy is peaceful enjoyment, and in fact tenancy is a legal property right, to access the property in question and do anything, without undue burden, allowed under the terms of the lease. It would be a violation of peaceful enjoyment for a landlord to allow vampires into the unit.

The right of inspection, by the way, is explicitly carved out in real estate law. The right to let vampires into the unit is, to my knowledge, not enumerated.