Under the laws of all states in this country the law presumes that if a person has signed a written document he or she has read and understood its terms in the absence of fraud. From what you have written, if you signed the lease that you just received notice on that a huge amount in back rent is owed, you should first have a face to face meeting with your husband about the situation. Afterwards, you and he should consult with a real estate attorney about this situation as to what needs to be done to rectify it.The landlord had no obligation to have contacted you sooner about the problem in payment unless the lease requires it.