We let out our spare room for almost 2 yrs.
We used spareroom.co.uk to find our lodgers.
They were all lovely, bar one, who was lovely, but my fault at not paying attention to the importance of finding the right person, iyswim.
The dynamic is very important. Work out who you would feel most comfortable with using your lounge, kitchen etc. We are a family of 3. We decided that female and under age 30 would work best. The lodger who was over 30yrs old just didn't gel with us, so my gut instinct was right. The younger girls were fab.
Set your rules...no boyfriends over (we have young DS), no family/ friends crashing over the weekend etc etc. You don't want to feel like your house has been completely taken over. But, they have the right to come and go as they please. Just need to be mindful when coming home late at night etc. Do they need to set an alarm etc etc...would u trust them with that?
Lack of bathroom would be problematic. Especially for the ladies/ girls. They spend hours in there! For our chosen age group the most important thing to include were a washing machine and broadband. Oh God the broadband we ripped thru! It was an eye opener. Allow for those bills to increase so you can take it into account. The website I mention above gives you all the info you will probably need.
Again, shelf in the fridge, shelf in the pantry or cupboard to themselves etc. Use of ironing board etc. Their own bathroom is always a winner.
Be prepared for bikes in the hall...hair dye on the bathmat, maybe...anything is possible! We didn't eat together really. Their hours were all over the place.
Young singles are never or rarely home. Those older or in established relationships will be in a lot more. Our last, older lodger was never out and camped in our kitchen all evening, skyping her boyfriend. We had to cook around her. DH felt really uncomfortable.
I said to each potential lodger, if your are unhappy here u can leave, and if we are unhappy here we will ask u to leave. Lodgers don't have the same rights as tenants. But good will and a positive mindset (and the relatively easy money) should make it a worthwhile experience.
We really enjoyed their company and do quite miss them.
Good luck!