Seems like that would be sufficient proof. 

Based upon this I would look at an actual dollar amount, not percentage that: 1) enables you to live in a safe neighborhood and decent schools district, is modest in size and fixtures, and has payments sufficiently small that you are still able to invest at least 10-20% (or whatever your target is) of your income. 

My guess is your original contract with the seller is not sufficient.

He agreed to join in investing with me and work for me for no costs at the start of our business (all income would be going back into the business until it's financially self-sufficient)On top of that HUGE benefit seeing as contractors absolutely drain cash during a rehab, my dad told me that he will possibly help financially support me in the start of my business.

I am primarily wondering how to best determine whether a particular single/multi family home would be a good candidate for being self-sufficient each month (outside of unforeseen maintenance & repairs) based on what rent is collected.

Consideration must be both legally sufficient and bargained-for by the receiving party.

If the deeds are not sufficient to resolve the issue (not likely), then order a survey.

The way mortgages are handled, the bank collects into the escrow account an amount monthly sufficient to pay insurance and taxes.

Also look at what assets your construction company owns. if you have very few assets and you have sufficient insurance then there is little to be concerned about in case of a suit against your company.

A 45 amp breaker (x 80% = 34 amps) would just be sufficient, but it would be cutting it close.