Rents are set by the rental market, not by landlord costs. 

I'm not saying you won't be able to raise rates. I'm saying that if you could charge 20% more on rents, then you are very kindly under-charging today. It has nothing to do with this change.

I have seen more than a few buyers - particularly of detached places - charge rents that couldn't possibly cover the carrying costs of the place, even if you had a 40%+ down payment.