Keeping Records - You must retain records relating to your property income for at least 5 years and 10 months after the end of the tax year to which they relate. Failure to do so may result in penalties of up to £3000 per tax year.

Rent-a-Room Relief - This relief is available to owner-occupiers and tenants who let furnished rooms in their only or main residence. No tax is payable if the gross rents do not exceed £4250. The exemption is split if the letting is by a couple.
If the rents exceed £4250 you have the option to pay tax on the excess or on the rent less allowable expenses. A claim must be made to the tax office if you want to elect to pay tax on the excess.

Investing in Buy-to-Let Properties - Interest payable on loans used to buy land or property used in a rental business, or on loans to fund repairs, improvements or alterations, is deductible in computing the profits or losses of the rental business.