Also make sure you understand everything about adding an ADU including value of the ADYPU, financing, impact from rent control, duration between initial expense and initial income, true cash flow (know the 50% rule, at 50% rent ratio initial property tax will be near 20% of income)- educate.  

True!  

We are real estate rookies based in the beautiful Seacoast area of New Hampshire.

It is true that you'll probably only be responsible for paying off the interest for the first ten years. 

Very True.

One seller was indeed making 90k/year in income however-they will never get a true license. 

This is true but they're also under market value rent by more than $1200/mo.

Real estate investing has become a true passion of mine because I love the idea of taking a run-down, neglected property and transforming it into a home where people can truly enjoy living.

I believe new construction homes don't cash flow as well, based on what I have read but not sure if true.  

Connie this is not true.. there about 15 states that require state license and NMLS in CA you can do HML with a RE Broker license legally..