"Rent lock" instead of deposit?

[Amy Davidson]

Hi all,
It's my first BP question, I hope that someone has some experience that can help.

I'm ready to buy a multi-family property that is currently rented, but most of the leases have something called Rent Lock instead of a deposit. The owner and wholesaler tell me that it's perfectly normal to charge this kind of initial FEE, and that it'll never have to be refunded by the potential new owner -- me. But when I Google the expression, and BP it as well, I can't find a single reference to it.

Has anyone used it or run across it? Any opinions that you'd like to share before I finally buy this place?

Thanks!