Tenant agrees to maintain the indoor temperature at no less than 50 degrees fahrenheit.

OxBlue has a guide to making your own construction time-lapses camera.https://oxblue.com/company/articles-and-blog/diy-t...If you need a rugged camera for outdoor use and you have the budget, they sell cameras too.PS - Go-Pros are more budget-friendly but they'll give your final video a fish-eye lens look

The temperatures were in the teens but will start rising above 34 in a day.

.- Safety Issue: The discharge piping serving the Temperature and Pressure Relief (TPR) Valve for the water heater should terminate not less than 6 inches or more than 24 inches above the floor.- Safety Issue: The openings in the in the basement stairway railing are large enough to allow a child to fall through.

It's in NW Florida, and near the water the temperatures don't fluctuate as much as they do inland.

In California, your source-water temperatures are unlikely to become cold enough that an in-line heater cannot boost the water temperature sufficiently.

I do like them taking care of outdoor maintenance, building maintenance, outside insurance, some utilities and some amenities. 

Adding on-demand heaters at point of use is often easier and less expensive than recirculation.Those same homes that "are not plumbed for recirculation" generally are also not wired for 240V in the bathroom (where the shower is), or enough amperage at 120V to sustain an electric on-demand tankless heater with sufficient capacity (after calculating winter drop temperature vs flow rating), much less plumbed for natural gas to support a non-electric model (which is the only type I'd recommend).

Or is my only (safe) option to get an outdoor tankless water heater?

I also have outdoor games such as corn hole, rope toss, etc... but my VR locations are good for the outdoors.