You can install a "whole house" surge protector in your service panel.

3.7MM capex, remodeling inside units, pool area, new gym, package lockers, fix and paint all exterior, resurface parking, pad cover parking, EV charging, solar.

The left panel has info on Total Value (the most recent assessed value) and Home Exempt. 

Currently I have fresh paint on the house (inside and outside), new doors (Garage and entrance), Solar Panels (10K system w/ LG Battery), and exterior aesthetics upgrades.

We had to do a panel upgrade within 3 months of buying the duplex, but it was something we planned for during the inspection & property analysis.

Updated, new roof 2023, new hvac 2023, electrical panel rewired 2023.

You could technically live off grid with solar

For instance, what is labor rate to install LVP flooring, installing interior doors, installing windows, interior painting, installing Romex, installing electrical panel, removing PEX plumbing and running new, removing trash, installing cabinets, installing counter tops, installing tiles and more.

The house had some old cast iron piping and older electrical panels and distribution.

Once you have all this documented you should know what wire goes to what unit, an electrician can then add a new breaker panel/meter and rewire to split the electric to the 2 units.