A solar/Finca is usually a plot of land with or with out a house, roads, electricity,sewers, etc. It could be a farm as well...These are generally in VERY rural areas....don't buy it UNTIL you see it!!!
Solar is a lot where you can build a house. Solar/finca is a lot in a rural area where you can build a house/farm and where is (some) space for farming or ranching.
Articles to help you in your expat project in Puerto Rico