Actually your expenses for each condo is more than 5萬. You supposed you do not pay any tax for the rental you get. But It is only true for the first a couple of years of your 25 years period. As time goes on, you would pay more and more tax for the principal in your mortgage payment.
For example, "貸款第25年,本金是$10243.10元,......". The 本金$10243.10元 of the last payment is after tax, is not tax free.