In reply to The New NickB:
Read about the law. It's better to find out what is what, in advance, rather than afterwards.
You must put their deposit in a deposit protection scheme, and if they then go and leave you no details of how to contact them, it can be a bit of a faff to get the money back out - you have to provide evidence of why you are entitled to keep it.
So - get them to sign an agreement about the state of the house when they move in, with photos and an inventory.
All soft furnishings must be fire retardant.
Gas and electricity checks must be done (gas every year).
If you want them to leave, this must be done in the right way. You can't just change the locks. There is a lot of advice about this online, but it can take 6 months to legally get someone out who just chooses to not pay their rent.
Make sure that you arrange regular visits, just to make sure that everything is going well.
Check the conditions of your mortgage and buildings insurance - you may need to change both in order to let the house out, and the insurance will be invalid if you don't tell everyone what you are doing.
You will need to fill out a tax return every year, so check what you can claim and keep all receipts.
Problems have to be fixed quickly. You might be happy to spend 6 months decorating a room in your own home, but this doesn't work in a rented house. You need spare cash and workmen to be able to instantly fix boilers, fridges, leaks etc.
Make it clear in the contract who will pay the council tax, contents insurance, water rates, utilities bills etc. There are lots of good examples online.
Be prepared for changes in interest rates - they are bound to go up soon.
Having said all that, you can end up providing someone with a lovely home and can benefit financially too!