Things like CCTV cameras, signage and exterior lighting go a long way with tenants.

I use a lock box, Wi-Fi thermostats and a security camera I can check on remotely.

Moreover, with the rise of digital nomads and long-term renters, you have a brand new clientele for international properties that pay high rents and give you 100% occupancy.

In summary, the main building:1) will need to be tented for termites/ants,2) will need basically two full bathroom renovations (floor around one toilet is a bit soft and rotted some of the joist down below, and the other bathroom is an addition that looks like it also might not have been built to code bc has really tight spacing and has a huge crack in the walk-in shower that basically just drains water out into the crawl space below the house and the floor under that area is just totally rotted out),3) would need a refreshed kitchen (sink drain plumbing is in need of repair and at a minimum would need new countertops but likely new cabinets as well)4) they recommended earthquake bracing to the foundation since it’s almost a 100-year-old house and reinforcing part of the cripple wall down below5) found a clog (or at least an area the camera couldn’t get past) in the sewer line.

We have trash day reminders, check-in instructions, house rules, check out instructions automatically sent to each guest.. it also changes the door code to the last 4 digits of the guest's phone number for each guest. 

However, 99.9% of the math you'll need to be able to do with real estate you will have learned by 8th grade.The real estate agent that just sold our house in NY could barely bang out an email and it would have killed her to have needed to add two 5 digit numbers together.  

This year home values have started to level off while rents are still increasing by double digits.

As off-cast cell phones come up hourly while your neighbors do their annual upgrade, you can have something personal with a camera and wifi (which works from the library, public stores and many other locations 24/7), you can open that ebay account and craigslist to sell off your freebie items gathered from society's refuse.  

@Andrew ReisPut a camera in the stairwells I bet they are smoking in the stairwells if they are smokers.

We use Minut for indoor monitoring, and exterior Ring cameras for exterior monitoring!