Private landlords?

Question

do they pay tax on the rent money they collect

Answer 1

Your avatar looks fearful. If even private landlords don't pay tax on rent money, the fright of  your avatar will make them to pay.

Answer 2

Yeah.  You need to register your self as a private landlord with your local tax office.  

You might have to fill in a tax return each year.

You will have to pay tax on all rent minus expenses towards the property. You can offset morgage intrest from your rental income.