So the TLDR version is that after sitting vacant for about 6 weeks in the winter with no heat or running water, we turned the water on at the meter and hear gushing from inside of the house.

The central heater installed is also electric, so either way, they'll have to pay more electricity bill because they pay their own electricity bills.I have more units in the property with exactly same heating system, but other tenants have no complaints.I am not sure what the minimum temperature requirement in Los Angleles, but if the unit can be heated higher than 70°F with central heater, do I need to fix the heater?

There are internal heating and cooling systems, electrical components, hot water heater, plumbing fixtures and a myriad of other issues that are hard to assess for the average home buyer.Realize that you are not going to catch every single flaw or defect on your first run through a home, although there are a few key areas that every home buyer should look at before making a decision.

There is moisture meter equipment and heat infrared technology to try and locate wet moisture levels and cooling and heat loss points.You might want an A/C company to go out there as well.

This is concerning with winter coming (heating), and generally the place is in bad shape and full of mice.  

Is there a heated dry cycle?

Annual Income 2017: $143,000 (10 1bd/1ba, 4 2bd/1ba, 3 studios and 15 stall garage)Annual Expenses 2017: $68,000 (includes $21,000 in repairs/capital improvements, $4,600 in heat, $7,300 in insurance and $17,500 in real estate taxes.

There’s baseboard heating around a majority of the room, so I feel like it won’t be an easy task.

Has the plumbing, heating, and electrical been upgraded?

People don't realize that even with proper grounding, something as simple as loose connections can cause excessive heating and thermal run away.