"The right kind of home insurance can either cover short term lodgers in your home, or longer term lodgers with formal tenancy agreements. In either case it will alter the way your insurer views your risk. For example, more people living in your home means an increased security risk or potential of accidents.
You must tell your insurer if you start renting out one of your rooms, as it could invalidate your policy if you're not clear who is living in your home."