Technically speaking, there is no limit to the number of residential mortgages you can have in the UK. However, lenders will want to check whether people are using them for properties which they then rent out. This is why most lenders will not permit more than 2 residential mortgages: one for your primary residence, and one to be used as a holiday home or a home in which a family member lives. When you apply for second mortgages for residential purposes, you will need to declare which is to be your main residence.