A new service panel should run you about $1500, what get's expensive if you have to re-wire the unit and fish wires to every switch and outlet, open walls etc 

You do not want to have open areas in a breaker panel where a tenant can accidentally get shocked while resetting breakers.Outside HVAC units look old but i doubt you will be able to get the price adjusted if they are still functioning well.All the concrete cracking/settling is normal... no worries Railing missing is an issue.

One of the most in-demand amenities in these properties is pet friendly units and common areas.A couple of panelists were from New York and with the new rental regulations that recently went into effect, many of those investors and developers are looking elsewhere.One common theme that seemed to carry across several panels was that many developers were having to "re-educate" their investors as to what realistic rates of return are today versus just a couple of years ago. 

Using extra long panels can help reduce seams too.

I also have significant HELOC, credit card, solar panel, and other debt.My goal is to rent out my current house, purchase an equivalent house with a big basement or mother in law, and move my family into the basement/apartment, and rent out the top of the new house.

new panel? 

The easiest way to check is to look at the amp rating on the main breaker in your main panel.

I have a client who has solar panels that are paid for on his house.  

There are items outside of that like roof, electrical panels, HVAC, etc that need to be taken into account for.

But some will not give you an easy online access panel unless you have some pricey business account with them.My local bank, with free business checking account, give me free full online ACH capability.However it is still your responsibility when you do a pull ACH to have written authorization from your tenant to do so.