I'm just getting started (one duplex in Nashville) but already I can see how it can be an effective tool to save more, invest more, and become financially healthy. 

I have story after story of the effectiveness of a mastermind.

If you were to offer them up to the investor community at large to fill in the gaps, that may fill some voids in their schedule.It's definitely been challenging for me to find reliable, cost effective labor in the area. 

36 year old newbie to real estate investing, my parents have owned a few vacation rentals and their large family owned ranch has branched out and now owns some commercial real-estate.I'm a visual effects editor working in Hollywood living in Sherman Oaks, CA.

Good article to read.http://bit.ly/2fqHT2f

You are correct that if it is left undisturbed there is no harmful effect,  where the issues occur is when removing them or if the are broken and the dust gets into the air. 

The most effective, so far, is co-selling, but eventually, I would like to be able to keep all my efforts.

The mindset for many lenders is, "if you have to pack a lunch for a site visit, it's outside your area of expertise," which at this point the deal is effectively a gamble.

I have two questions.(1) How does that effect the underwriting and ultimate mortgage I may obtain?

Having a MA construction license allows me to be cost effective for up-fits or remodels so a flip here and there is always something I am looking for as well.