I'm about to start my first rental property and has solar panels. 

Changing electrical panel or changing all the wiring in the walls?

In this time I learned to hang Sheetrock, install and finish floors, take out a load-bearing wall, install copper, pex, and drain plumbing, wire a house, install a electrical panel, and every other possible task in between, and my father and I did all the work ourselves.

wood panelling, shag carpet, etc...   

For comparison:Currently working on a 1350sf SFR, needs full perimeter excavation and foundation repair, tear down garage and rebuild (including footings), driveway remove and replace, gut kitchen and 2 bathrooms, minor wall repairs, paint, flooring and light fixtures, new electrical panel, furnace and air conditioning replacement.Total rehab cost is $56,000.I couldn't imagine your property needing more work than this, which leads me to believe that you're contracting your repairs out at a cost that prices you out of the property. 

I initially paid for repair but the repair job was not good at all - this was a lazy Susan cabinet door, the repairman tried to bond the two panels but there's so much gap between the two panels and paint has chipped, they're so ugly. 

About $600 per unitOther miscellaneous expenses: drywall, 2x4s, trim, framed mirrors, caulking, sandpaper, screws, finish nails, various tools, etc.Oh and fence panels & materials $1400 total for all units; we deducted a total of $750 from the first new tenants rent over a period of 3 months to install it.Well that's my story, I would love to hear from others who have similar goals and experiences.  

Once the electricity is turned off outside the house, all those wires in the electrical panel are no longer live - but they are still copper.

That's why I put together a panel of property analyzers in the market, boots on the ground and they know the neighborhoods street by street and have their pulse on the market.I agree that random OOS investing where the investor is trying to do all the research and estimating on the numbers is SUPER dangerous. 

Installing solar panels could generate more passive income, but it wouldn't come directly from tenants