Main things you would be concerned about would be an old panel with screw in fuses or one of the old breaker type panels that are known to fail.

You would probably be looking at $5000+ for a heat pump that would do heat/cool.Electric baseboard heating has electrical load requirements that may exceed your current panel capacity so consider that as well before going one direction or the other.

They hired their electrician pal to put in a new electrical panel for about $1,000 on a weekend, calling it an emergency, when the only problem was that the tenant was trying to plug too many things in at a time.On and on, to the point that about $6,000 of reserve money was stolen over about a 3 month period of time. 

And since everyone in the house didn’t have access to the electrical panel and water shut off.

I was listening to a panel of large multifamily operators in my market and they reported service calls are down substantially.

One easy, quick check is to see how many Water meters/services there are, or how many electrical panels there are.

If you want to do everything yourself look at the list above and start putting together all the things you would need, the subs you would manage, the materials you want for finishes, if you are upgrading panels, plumbing, windows, or anything major familiarize yourself with LADBS. thats what immediately comes to mind without knowing many details of your purchase or your goals. edit: Rum comps for rehabbed duplex in the area, see what budget you may be able to refinance into in 6-12 months. if there are tri or quads in the area then consider an ADU(or two) on your lot. consider the square footage of your comps and what opportunities you have. read about ADU laws and familiarize yourself with the opportunities. 

The neighborhood and surrounding areas have tons of homes with solar panels.

Maybe even look into some vinyl faux stone panels if they are cheaper so they don't stick outward from the wall / stairs.If you go too specific to a taste too it can turn someone off & have them think, 'well thats one thing I have to replace' that is not my style

I find that most WA state credit unions like solarity, red canoe, verity, salal, and many other credit unions is that you'll get up to 10-15 year terms adjustable every 5 based on an index + margin.