Down payment assistance programs are frequently used to help NACA members buy down their interest rate. These programs consist of a grant to the homebuyer, not a loan, so it would in no way be considered as second mortgage.
I talked to my local down payment assistance program and was informed that it is in the form of a second mortgage, and that they will only allow you to use the funding toward down payment and closing costs. Can you recommend a down payment assistance program that will allow you to buy down your interest rate?
There are literally hundreds of programs all over the country. Many are specific to a local community, so you will have to consult with your MC on that one. The local office should have information for programs in your area.