I will be occupying one of the duplexes and would like to purchase the remaining 4.

Both parties would have to sign the amendment.Before you do this, ensure that the remaining tenant is capable of carrying the lease on their own.  

@Kyle H  one thing to keep in mind is we all kind of knew the market would rebound.. and that 2008 to 2012 prices would not remain.. so I think that goes to the strength of the market your in...

As I do not have much of any commercial real estate experience, its good to get the input from those which know this market and know the key 'pinch points' for evaluating a mixed use property like this one.I obviously let this one alone, however the property remains on the market and most recently dropped $200K; Cap Rate has now improved to 7% with 3% total vacancy loss; 6.5% with a 10% vacancy loss.

If a material item remains unfulfilled or is deferred until some future time, the contract is "executory."

I definitely feel this is much better than I can get in the stock market, and these numbers tend to auto-adjust to inflation, which the stock market does not.  

Step 1: Buy just 4x $20k properties (carefully sourced in hard-to-find sweet spots of say, the Mid-West) and rehab them with your remaining cash, and of course, rent them out.

I paid Sense Financial for setup documentation, and there's an annual fee to remain compliant, but that's about it.

Last year we were able to knock off 15 years on a different mortgage by paying extra on the principle, we now have 13 years remaining after 3 years into the loan.  

His rent is ballpark fixed relative to inflation based on rents 15 years ago, at the expense of his personal landlord.His investment properties are all in cities that do NOT have rent control.