Does the fact that I was unemployed for 4/12 months in 2017 affect my rental income tax calculation? Would the tax rate on the rental profit be at the lower rate potentially?
Possibly - you will be taxed on your total income for the 2017.
For single people, income up to € 33,800 is taxed at 20%, anything above that is taxed at 40%
For a married couple, income up to € 42,800 is taxed at 20% and anything above that is taxed at 40%