My heart rate goes through the roof as I have about $90k in equity in that house. 

I still have a roof.

If it is recorded as built in 1920, that is what the insurance will be based on.The most valuable update with regards to insurance is the roof. 

Our plan was to rent it for 3-7 years, and then sell it, before a roof, HVAC, plumbing, or even much flooring was in need of replacement. 

., new roofing, foundation repairs)-Cosmetic Enhancements (e.g., new flooring, updated bathroom/kitchen fixtures)-Energy Efficiency Upgrades (e.g., solar panels)-Accessibility Modifications (e.g., ramps, widened doorways)-Luxury Items (e.g., pool)-LandscapingNot Acceptable Renovations:-Commercial Use (e.g., turning a residential property into a commercial property)-Temporary Structures-Non-Residential Buildings (e.g., barns, stables)FHA 203(k)Minimum Down Payment: 3.5%Minimum Credit Score: 620Minimum Loan Amount: $50,000Maximum Loan Amount: $524,225Occupancy Types: Primary Residence ONLYUnit Maximum: 4 UnitsAcceptable Renovations:-Structural Improvements/Reconstruction (e.g., adding rooms, bathrooms)-Cosmetic Enhancements-Eliminate Health and Safety Hazards-Energy Efficiency Improvements-Major Landscaping (e.g., grading, tree removal, adding walkways)Non-Acceptable Renovations:-Luxury Items-Commercial Use-Temporary Structures-Non-Residential BuildingsBoth of these renovation loans are similar in many ways, but the key differences are:1.

I hopped on the roof with the garden hose to defend the property (even though initially it was contained) when suddenly an ember spread to a palm tree (that had been neglected to be trimmed for years) that instantaneously atomized/vaporized into hundreds of embers and spotted fires on several homes.

Estimated cost for remaining changes (all new electric, drywall, tile, fixtures, cabinets, roof, doors, windows, heat pump, some siding, and fencing.

Old properties aren't a bad thing as long as you account for the big four- HVAC, foundation, roof and sewer.

I have however feel victim to some pretty steep bills for property taxes.  

The owner also needs to save for big ticket items that may need to be replaced every 10 or 20 years such as AC, hot water heater, furnace, roof.