Two of your questions will be more situational and location based.We don’t ever haggle on pricing, although I would suggest being flexibleWe check credit, criminal history and everything that goes along with that, evictions, and income.

i set strict qualifications for my rental 3x income credit score of 700. 

Have you leveraged lines of credit, private lenders, portfolio loans, or other creative financing options?

My business partner owns a roofing company but has weak credit and more limited cash flow.An LLC is a common choice for partnerships since it protects personal assets and simplifies tax management.

For context I am a full time lender and understand DTI and have very good credit. 

So for example, a 761 credit score will be in the 760-779 credit category, then going down to 740-759 and so on.2.

Once we had the home inspection I was able to have the seller credit us at closing $8k...of which the escrow could not credit the entire amount and so I had the seller write up a personal check for $2000 How did you finance this deal?

Given your credit score and ability to fund 25% of the purchase I don't foresee any obstacles you will face. 

One of the benefits is that being on the loan can help build his credit, which will be valuable for his future financial goals.

For example, I mention that every adult must pay a $30 application fee, pass my credit/criminal background, make a combined income of 3x the rent, and whether or not the property accepts pets.