Hey, I'm an amateur vampirologist. Feel free to tell me to go F myself if you disagree, but here are my thoughts.
In most media I've seen it's not the property line, it's specifically the house.
Subletting leads to an interesting conundrum that I'll have to explore more but on its face I think it checks out. I also think it's very silly and would love to see a work that explored this.
As I understand it, you'd have to build them pretty close together so it couldn't escape, especially if it can turn into mist or fly, but theoretically I think that would work too if you could build fast enough.