Lucky you if you can get the landlord to sign a such paper. And of what value will it be in case of disagreements? The Chinese attitude towareds contracts differs from our contract culture in the West. Ask for advice first whether it would be appropriate to ask for such a thing.
Think cross-culturally!

Thanks for your advice, I will try and box clever in that case. But I think you'll agree that if the landlord can, at the end of your contract, make you buy him a new washing machine and a new AC to replace the ancient ones that have broken down, you could end up in queer street. I shall have to get my thinking cap on, or ask Star (sausage man's wife) to get hers on and word such a codicil to the main contract diplomatically.