I would recommend starting with How to Invest as a general overview, then diving into Rental Property Investing for more detail.Both can be found at biggerpockets.com/store.

I’ve started to dig deeper into probate whole saling.

Apartment complex investing has been an interest of mine for quite some time, though i knew it would be best to conduct a thorough research before diving right in.

I feel I'm 85-90%% there before diving in, maybe a week or two. 

If so, you need to dive into their numbers and get each income and expense category, determine if that is how you will operate the property as well. 

If you want to determine the debt coverage ratio, its simply diving the total net operating income by your debt service (principal + interest...

Nor would I want to pay an electrician $400 to change a breaker, or even more if it's an emergency call.I think maybe the best thing to do is just dive in and see what turns out to be the best way to do things.

The deeper I dig, the more I find I know nothing, lol.We have 3 "passive" investments with a local company in the apartment business.

Get the Zillow estimate, dived by 3 and place that value in the form. 

They certainly have deeper pockets for legal fees.