Run, don’t walk. If your purpose is to buy something together that someone else rents from you and pays the mortgage – that is an investment. If you buy something together with friends that you want to use yourself each for a month and then rent out … it’s full of unintended consequences. 1. The lovely friend family loves things neat, washes dishes every night, vacuums and cuts the lawn – your family is the opposite: trouble. 2. Children are different when they are supposed to listen to a neighbour. 3. All expenses become a problem. If you do, sign a clearly laid out JV agreement, even if it is your brother (particularly when it is within the family).