I've seen a lot of people renting rooms out in their flats for what I imagine is basically their mortgage halved - either that or 'market rents' has meant the end of being a lodger being a cheaper option and people have realised they can charge £800+ for a spare room because that's how much a houseshare seems to be here these days. On the one hand, it's a sensible thing to do ifor the owner f you're struggling for money and have the space, people need places to live, and at least there's less likelihood of your room being affected by damp and mould. On the other hand, being a lodger means fewer rights for the tenant than a houseshare, and it is a bit galling to think you're paying your housemate's mortgage but could effectively be kicked out tomorrow.