Rental income from rental properties is considered to be passive income which is where you make money without doing much work and the money just flows in.
And on taxes passive income cannot usually be deducted on the tax forms as a loss like non passive income sources could be.
However as long as you're actively participating in the rental income then there is a special rule in the taxes that says you can deduct as much as $25,000.00 as a loss on the rental property.