Unfortunately a landlord is allowed to refuse to go month to month on a lease. I assume nothing in your current lease states that you may go month to month upon completion and if it does it usually leaves it up to the discretion of the landlord.If the landlord is insisting on 6 months or that you move out he does have the right to do so. You should try to talk to him and see if anything can be worked out. You also can always call a local attorney and ask them for advice. I am not admitted in AZ but assume the laws will be the same in that regard however there may be a caveat that a local attorney can point out and it is worth a phone callgood luck