How do I figure out exactly what interest rate I will be paying if I including taxes and inflation?

If you are already going to invest the 8k, what better way than on real estate. There are 1 or 2 ways that would be best. 1. Pay it now and have more equity later because the balance on your mortgage will not go down for the first 1 to 2 years on a fixed loan. Or 2. make your regular payment and then the same month make an extra payment of the 8k that 2nd payment goes directly to your balance.