I don't use a co-host, but I would expect to pay for any permanent improvements to my property. 

I'm ready to move on from this tenant, fix the place up, and improve the asset. 

This tax credit is a federal benefit that saves companies money for implementing activities such as improvement, design or development of software, processes, formulas or products.

If you spend the time, you will expand your connections and improve your knowledge.

However, I've also been reading about BRRRR investing and I'm considering the idea of doing some property improvements and doing a cash-out refinance, but I've heard that some lenders aren't doing those loans in Texas now because of the fear that the prices are on a bubble that might burst, which makes me think perhaps we could just reconsider selling in the next six months when we're ready to leave, if the theoretical bubble is still around. 

The numbers work, and will improve after I raise rents to market rate next Spring.

What makes you think they will suddeny improve?

As for the rest of your questions (2) I'm open to all asset classes with the focus being on the "right" type of asset to maximize depreciation (I.e. more value in improvements relative to land cost since it's not depreciable)

The IRS treats billboards as improvements to realty.

Each of those properties has a basis that is determined by your purchase price + capital improvements - depreciation = your adjusted cost basis.