Taking in a lodger has fewer legal requirements than letting a whole property. However, we'd always recommend you put something in writing as it'll protect both you and your lodger and give you a basis for reference should any disagreement arise.
A Lodger Agreement is used when a landlord wants to rent a room in a furnished property where the landlord lives and shares common parts of the property (e.g. bathroom, toilet, kitchen and sitting room) with the tenant or tenants. If you want to rent a room in your flat or house, then this Lodgers Agreement can only be used in situations where the property is your principal home.
The SpareRoom lodger agreement is produced by the Guild of Residential Landlords and is suitable for landlords in England & Wales (for Scotland, click here). It's available for just £7.50 for the pdf download version, and £9.99 if you want us to send it to you in the post as well.