There is so much to learn between the ages of 18-22. 

My question is: could the current tenant (age 59) remain in the property if she becomes eligible for Section 8 assistance?

Getting started in commercial real estate investing at your age is a commendable goal.

They are starting to age out.5.  

Many of us on here wish we were thinking about real estate at that age.

Ranking in order though...1) Prices will drop - 10-20% because the job market is getting tougher2) Salaries will increase - 3-4% per year to keep up with inflation3) Interest rates will drop - 100-150bps as people worry less about inflation4) Unfortunately, the dream of a house with a white picket fence will be out of reach for many, especially before the age of 40.

You start by mentioning your age... you'd need everything to go just right for the rest of your life to make, best case, $400 or less additional each month net cash flow. 

Congratulations on building such an impressive portfolio at such a young age and achieving so many successes!

For (2), as properties age the rents you command decrease. 

Also, I am thinking of investing into real estate via a new Self Directed Roth Solo 401K account due to tax free distributions after age 59 1/2 instead of SEP IRA, any thoughts?