Lates on a mortgage trade can impact your ability to get loans in the future. 

Two flats are essentially just houses.... they trade like houses and there is a lot of emotion involved.

You could try to value it with the income approach, with NOI & DSCR, but that usually isn't done with smaller multifamily.You're going to have to extrapolate out farther and see where other smaller multifamilies have traded.

Have you executed these strategies somewhere else already?

Congratulations to you for setting yourself a goal and having a plan in place to execute it. 

I traded up for a 7 unit apartment building.

Day traders are not exempt unless they elect mark-to-market (MTM) accounting, which eliminates wash sale tracking but taxes gains as ordinary income.To manage taxes, track trades closely, avoid overlapping purchases, or consider MTM election if trading actively.

After reading Brandon and Brian's book, The Multifamily Millionaire, Volume II: Create Generational Wealth by Investing in Large Multifamily Real Estate, I'm a bit puzzled as to if the GP's must have real estate experience, or if someone can connect enough professionals/companies on their team to execute successful investments.

I would read up on "Squatters Rights" laws and how long a typical eviction takes to execute.

If you're more of a 'personal referral' person than a 'do research online' person, and this is local to you in Manhattan, KS, hit up one or two of the trades people in the "little apple all stars" BNI group.