The mortgage is totally open. You can pay it off at any time, no penalty.
However, it is commercial mortgage, interest rate is much higher than a residential. The interest rate is prime rate plus 1%.
You have to pay realtor's fee for each unit. Tax is different for each person.
I tend to forget about the tax, because I cannot avoid it. If I want to keep more, I have to make more. You can only deduct so much on tax, after a point, you cannot deduct anymore.