What are the typical vacancy and repair rates are you seeing for post repaired buy and hold rentals in these areas? 

There's no way they can know what investors are spending or their holding costs between the purchase and resale of properties.  

My main real estate goal is to own an apartment complex using the buy and hold strategy.

I believe it can and will hold some value for you still.

To meet this objective you have to consider your All-in Costs (Purchase price, Rehab Cost, Holding and Closing costs).   

I know that in MO, you've got to have a couple of years behind you as a "Salesperson" before you can get your Brokers license (and thus have your own PM company) - but as long as the partner who has their Broker's license is willing to hold your Salesperson's license... you can manage as a fully legal PM to your heart's content.

Did the structure they helped set up hold up and protect you in an actual legal situation?

I've done 5 buy-and-hold deals personally over a long period of time and I'm looking to ramp up my activity significantly.

How long should you hold on to a property before selling from a financial aspect?

Because I started my own business and had to show two years of positive income within the business my wife and I had to hold off on buying our first house.