With the Homepath loan you are looking at 3% down if it is a primary residence and 10% down for an investment property. So, unless you will be occupying one of the units you will need 10% down. The important thing to remember is that there is no PMI which saves a lot.
Feel free to contact me personally for more information, I am right down the street in Hanson and I've done quite a bit of research on this area!
If you'd like to deal with a local (Mass.) lender on this or anything, please feel free to contact me. Our main office is in Walpole.
Thanks, and good luck,