If you have previously recommended this thread, you should see a tick / check mark on the recommend button. Click the tick to undo the recommendation (the tick may appear to change to a cross as you do this.) If you added a comment with your recommendation, you will need to delete that from your facebook wall separately.
Just to add to work out worst case of what you pay tax on so assume house is rented for 12 months. Total annual rent less agency fees, mortgage interest and insurance. That should give you a rough idea.
If you already pay PAYE through employment and your profit is less than £2.5k they can adjust your tax code to collect the tax due from your rental property. You get sent a form each year to declare your profits.
If you have a profit of more than £2.5k you will need to fill out a self assessment tax return.