If that doesn't answer your question sufficiently, perhaps it's because your question isn't very specific. 

For the ones that have sufficient equity I would reach out to the seller to try to buy it, and if all else fails, I could try to buy it at auction.

Aside from just property's zoning which dictates the quantity allowed, there are the other site requirements and restrictions.As far as efficiency, a small apartment building would likely be the most cost effective for the most units.

While this will be a 1031 deal, the buyers of our property are willing to be flexible re the closing date to give us sufficient time to find replacement properties.Would love to receive feedback on any of the above markets or any others that might meet our criteria. 

I would focus on quality deals verse quantity.

If an installer cant explain this to you sufficiently, shop somewhere else.As for the home value, I would agree that an additional 100k for solar alone is highly unlikely/ nigh impossible.

I don’t have any other hesitation other than the total income they receive from their jobs not being sufficient (at least 2.5x the monthly rent), but should I consider the six months advance rental payments knowing they will have access to additional income made from the sell of their home?

Then you manage the property for a year, at which point you should have sufficient documentation for a bank loan, & pay off the seller-financed loan.

Investors are always looking for:Doing more deals at once (quantity/capacity)Getting more profit per deal (margin)Doing deals faster (time)

Our income is not sufficient for us to take care of our family so we would like to get into real estate to help us build wealth for retirement and college funds for our kids.