zero rent to family

Tax Planning and Financial

I own 2 buy to let properties ( mortgage free). One of the properties has been let to my daughter for 4 years. She recently married and had a child. I want to allow her to live in the property rent free for a few years while they save for a deposit for their own place. My questions are 1) Will HMRC allow me to declare a zero rent or will they expect me to declare a ‘notional market rent’ ? and 2) if i am allowed to declare zero rent on this property, am i allowed to offset maintenance costs of both properties as a single figure against the total rent of the 2 properties or do the 2 properties have to be treated seperately i.e. maintenance costs in a certain property can only be offset against income from that property. Many thanks in advance for Support Team advice and relevant member experience.