We have built a database based on room prices from various roommate leasing sites. 

I was driven through 38111 zip code by a local, @Alex Craig and he explained street by street how different the houses, tenant base and rents were.

There are only three instances where it makes sense to buy solar panels for your house.1 - You are living off grid. 2 - You live in a state that has sky high electric costs AND great tax insensitive.3 - You have lots of money, don't care if you are paying more, and want to feel like you are saving the planet (even though you really are not). 

For these investments, if they are both properties you are able and willing to buy, I would make a decision based on revenue/expense assumptions.

What's the play here?

Land is a solid investment as an appreciation play.

That’s all rhetorical of course, but what role is Airbnb playing in all this?

I have played around with both Reanomy and Costar as well as pulling lists from the MLS then trying to skip trace them. 

I have a credit repair team already in play doing what they can to see how far up i can get my score from all three 621,647,661.

It's a block-by-block play that in my opinion & requires a visit so you can determine where you feel comfortable and also to ensure that you situate yourself where shopping (grocery shopping) is closely available.