If you paid in cash, you do not have much recourse. Your landlord is not legally obligated to provide a receipt. My guess is he/she is probably doing this because he has not been reporting your rental monies as income. I suppose if you wanted to press the issue, you might discuss the reasons for not providing same; and perhaps mention or imply tactfully that in the eyes of the united states IRS, not reporting rental income/income tax evasion is a federal offense, carrying stiff fines and penalties, --and perhaps even prison time. Be careful how you mention this, however, as you are likely still beholden to this person for a place to live.

If this is the reason you are not being provided with a receipt, you can reassure your landlord that the purpose of your asking is to qualify for a housing loan.

Other than this, you have little recourse except to demand a receipt for future cash payments, or make them in a form that is trackable and doesn't rely on your landlord, like money orders or checks.

Good luck. I'm sorry your landlord is being a jerk to you, and hope you have your own home soon.

 Then you can sue against him in the court for the same because this can be legally enforced and he is not giving you receipt in order to avoid taxes he has to pay.