If an enclosed building isn’t allowed, ask about solar covered carport or commercial equipment parking/storage (ie plows in the summer, tractors etc).  

Something to pay close attention to is making sure there is a separate owners panels in 3+ unit properties.

Hello,I have a single family house in Northern California which is my primary and it has solar panels.

If they want to sell now or in six months, you need to know before giving them an offer so you don't lose leverage by giving them an offer now instead of closer to when they are ready to finalize.Since you are already going to the property, take good pictures and make sure you capture the electrical panel, HVAC labels, and plumbing material.

First floor and the existing bedrooms were just updated with new paint and faux paneling.

Very good lighting inside&out (on a timer), plus motion activated lights as much as possible/appropriate (they make super bright LARGE led ones, even solar now so don't need to be hard wired). 

I have identified solar farm developer for my vacant lot.

I'm worried this is now going to be yet another massive expense.It seems to be a single meter panel with 10 - 12 meter bases is very $$ and hard to find.

@Sam GhiHave you considered buying raw land doing a solar farm, cell phone towers, or micro grid.

In Riverside you'll have to install a panel and meter on the ADU.