Ductless mini split AC units

[Kyle Smith]

Hi recently bought a duplex with window ac units.  I am looking into getting three heads for "ductless mini split" for the back house of the duplex (one head for each room).  Do you all think this is the way to go? Also, does anyone know the size i should get for a 900 square foot residence.  I have also received different feedback on how many heads maximum you can use for one condenser.  Any help would be appreciated !