MF home, one heating system, 3 heat zones.

[Allison Park]

Hi everyone, I had an offer accepted on a MF home in Somerville, MA. It's an older home built in 1900. Currently has one heating system (hot water baseboards) for both units, but there are 3 heat zones (one for unit 1, and 2 for unit 2). How easy would it be to split the heating system into 2? Have folks done something similar and what did it cost approximately? We've heard it should be easier since there are already 3 heat zones, but curious to hear others experiences. 

Thanks!

Allison