I have a scenario where there is an overlap with (current) outgoing tenant move-out and incoming tenant move-in dates during the middle of Jan 2022. 

@Dave Spooner Absolutely, the potential of decreased turnover from having a more desirable up to date property can also have a large impact on consistent cash flow!

Depending on the state laws, your tenant may not be able to get rid of his guest at a later date without going through an eviction -- would be good if he knows that ahead of time and has the tools available (ie guest being a subtenant, not a "regular" tenant). 

You may be able to get a non-refundable option payment from the tenant-buyer and can potentially contractually lock-in a premium above the market value on the future sale, which may prevent you from losing money on the resale, if the buyer can actually complete the transaction at a future date.

Short term rental apps are starting to pop up for boat slips. 

There is no reason to get married without dating first. 

My county has very up to date aerial images.

Any suggestions on pool heaters or devices that work with heaters that have app / connection to be controlled remotely?

Keep a mileage log, there is an app for this.

Pay them about $300 to $400 to do a table top app.