Not to be intrusive, but I would love to see what types of properties and what you are figuring for numbers.

We are talking about rental properties, not government surveillance of your smart phone or some other privacy intrusion.

I agree with moisture intrusion being high on the list and causing a host of other problems as you delay repairs, but do you have an opinion on other repairs that have a similar trajectory in the sense that they get more expensive/cause more damage the longer you hold off?  

Also, the game room we planned has water intrusion issues due to the low elevation. 

I'm looking for insulation, water intrusion (after having already looked for clues outside), and systems like a sump pump and drain tile in the Midwest. 

You have to watch out for knob & tube wiring, cedar posts that cause floors above to tilt, water intrusion from fieldstone foundationsRents at Covel St appear to be $100 to $150/month below market. 

Root intrusion at leaded joints.

I echo the above advice to make only the minimum basic repairs: fix the leaks, get rid of the mold, clean it up, stabilize it so water intrusion and whatever issues it has aren't getting worse, maybe do some demo to get rid of major eye-sore areas, slap some paint around strategically, remove trash/overgrown bushes and whatever from the property, improve the curb appeal however possible, apply turd polish liberally... whatever you can do with as little money as possible to make it look a little better, and then wholetail it like a hot potato for whatever you can get. 

And since this is Florida, there is a mold issue that could come from water intrusion like that which is also a problem.

They are not intrusive, but they give me a better idea of who they are and usually the guests pony up other info.I ask have they been to the area before, are you celebrating any special occasion and are they bringing a dog.