Rental Income and taxation

My wife and I have a 2nd house that we are planning to rent out as the sale fell through and we were wondering what the tax implications are? My wife currently gets Mortgage Interest relief on this house, so will it be affected?

There are a number of threads on rental properties on AAM, a search on "rents" "mortgage relief" might help. But basically TRS is no allowable on a rental property. The interest is allowable as a deduction from rental income, along with other expenses like insurance, repairs, etc. Interest is only allowed as a deduction where the property is registered with the PRTB.