Rental income receives better tax treatment than income earned from wages — you don't need to pay FICA taxes on rental income, while you do have to pay FICA on wages you get from a W - 2 (and
double FICA on self - employment income!).
As such, you are essentially having to pay tax on this 2 times cause not only did you pay income tax on employee portion of the
FICA taxes, but you also end up paying taxes on 85 % of the
FICA benefits, hence
double taxation essentially.