Perhaps you were mistaken what you actually signed, and I am not judging your statements here, but if you signed an original lease agreement and if it does not state that the landlord has a right to change the deposit for other circumstances, then the original agreement is valid in any court and you would not have to agree to a new agreement where you have to pay double the deposit. Make sure you read the original fully and understand exaclty all the stipulations. If it were in fact a "lease agreement" and nothing in it states that the deposit can be changed after the signing, then your landlord is obligated to obide by the agreement just as you are, and in no way can they keep you from moving in and/or evicting you because of not paying the extra amount on the deposit. Of course, if you haven't moved in you are better off frankly to find another place, because it will cost you more time and money to file a civil case against them than to just find a new apartment/house. If the potential landlord is shady about agreements, then unless this place is the Taj Mahal for free, then they will probably give you more problems in the future and no one really needs that.