The land is Residential Agriculture but I wanted to try to build a duplex or expand the number of bedrooms in the unit.

In PA, basement habitation is not allowed if any basement wall is below grade or if the basement exit door to the outside is below grade (PA 6400.81).

A duplex in one state, and 8 units (3 single family, a triplex and duplex) in another. 

At Neu Real Estate Group, we specialize in vertical development, particularly new build duplexes in the Indianapolis market.

but in the short term (2 years), we have enough cash and plan to buy a 4 unit and enough equity in my first duplex to buy another 4 unit.

It is an older home, and would be hard to move walls around to make space without basically taking the whole house apart.

In Mass, that means that all components are double-wall, non-corrosive (fiberglass). 

It is a duplex that needs considerable cosmetic work on the one side.

So if you sell your property you could get a duplex or multi-family somewhere with a more attractive market.

Zillow - for sale by owner (all single family on Zillow), Apartments for Rent by owner (usually small duplex or four plexes - call the landlord and ask if they are thinking about selling.