Renting a spare room has a number of benefits, but is not risk free. Would be landlords need to consider:-
1. Will their house and buildings insurance cover damage caused by "lodgers".
2. Is permission required from mortgage lenders?
3. Are there any restrictions on operating a business from your home?
4. If you have a leasehold property you may need the freeholders consent to sublet and this may entail paying a fee.
As a risk averse lawyer, I would always advise clients to check their position before accepting a tenant into their home...and even then consider taking out landlords insurance...just in case you need to sue tenants who abscond without paying rent or damaging the property.
Landlords can now earn £7,500 tax free when renting out spare room