First off, I commend you for jumping in at a young age and focusing on multi-family. 

Expenses:  Because of the age of these homes, they sometimes need roofs, kitchen remodels, etc.  

It's totally up to you but I think very few investors would suggest less than 7% on anything with 20 units or less.As for repairs, the 10% you have total is for reserves (I think these are actually pretty good numbers depending on the age of the place).

@Mario Reguera one of the best ways at your age is to find a cosigner.

My goal was simple, increase income to the point where my personal budget was at equilibrium and I did not need to withdraw from retirement savings until age 65.

Good Luck and please let us know how it turns out, I wish I had been as smart as you are at your age Call your parents and thank them!

My goal is to build up enough cash flow with adding additional rentals(15-20 rentals paid off) to one day being able to afford a vacation rental and renting that out until I’m at retirement age.

If the vast majority can't handle it, and their average age is 20 years older than you, the odds of you making it are extremely slim.I hope you educate yourself on the job and the costs and that it works out for you.

I would like to do the same thing (retirement aged and high % of equity homeowners) but was curious as to how you found these people.  

Louis is a very mixed area and we know nothing about the age of the buildings, or location, or condition, or neighborhood.