Do you figure mortgage payments for a 2nd mortgage the same as for a 1st mortgage?

We’re about to close on a house and we have a 1st mortgage, and then a 2nd to pay some of the down payment. This avoids PMI. If I plug the numbers into a mortgage payment calculator, the 1st mortgage payment is the same as the one on the TIL the lender provided. But the [...] http://bit.ly/m76dJV