keewee01: If they are putting it up due to the extra person and the wear and tear they will generate, get that in writing.
I suspect you would then have a very, very good case against them for the fact that you are paying 3 bedroom rental rate (which was the rate advertised when you took out the lease) and yet there has been only 2 of you. Therefore, due to the less wear and tear that has been incurred on the property it should have been leased to you originally at a lesser rate and your want a refund!!
They couldn't possibly argue with you on that as it is the same argument they are now using to increase your rental.
Of course, if they are only increasing it by a minor amount, then it isn't worth it. But if they are increasing it by $50 a week or something, then they should be refunding you that amount also for the time you've been there already!!
it doesnt really matter much what was being paid before, and what they ask now. if you add a tenant, where the current lease limits you to two, the the landlord can simply say "no", or offer to renegotiate the lease or lease agreement to add the third person. if you get to renegotiate the lease then any prior rents or rent rises are no longer applicable as you're basically starting afresh.
if the lease states "maximum of 3 occupants", then you can probably just add the extra tenant without concern - unless there is some clause that lets the landlord vet -all- tenants before allowing them.