0 Votes. For the average person looking to build a solar farm on their farm or flat plot of land, the initial investment can be as low as $20,000 to $40,000. You will also be paying plenty more for the instillation, varioius extra equipment, and power lines. Votes. The cost of a solar farm and the economics of how the solar farm operates will differ drastically for arrays of different sizes and depending upon geographic location (i.e. due to varying insolation levels and relative availability of PV/solar equipment suppliers).