You'll need to upgrade to a minimum 100amp service and I suggest going up to 200amp as there is often less headache with inspectors and it will cover any additional electrical needs in the future that may arise.

Making extra payments is always a good idea when you have a higher interest rate, that allows you to use the money you would have put down for some upgrades or needed work.

That is the time to do repairs and upgrades to get the the unit rent ready again.   

If the market maxes out at a certain rent with standard fixtures and finishes and no washer and dryer for example, it does not make sense to upgrade units to premium level and add washer and dryer if you can't increase the income and ultimately the value. 

Is the building going to appreciate over time and from the repairs/upgrades you do?

Major cosmetic repairs and upgrades.

No need to make unnecessary upgrades.

I've done big upgrades such as two complete bathroom remodels, kitchen upgrades, some new doors, outlets, windows, plumbing, and more.

I would manage the property and do upgrades over the next few years to increase the value while initially pulling ~$750/mo net income after factoring for all expenses. 2.

I have over 50 units now and I can tell you the most difficult one to ever rent out was my first personal residence when I upgraded.