I guarantee you will be able to find two houses in NC for the price of one in NJ.  

You can never guarantee that you will avoid going to court.

Then the LLC (with personal guarantees from partners) bought the rentals with bank financing.

You'll be getting top dollar rent since you will be paying per student rather than for the whole unit, you won't have to worry about missed payments since the lease is guaranteed by the parents, and you won't have to worry about vacancy because when they move out, they get their friends to move in.

Is there opportunity here that I'm not seeing that others can help me to see, or can someone throw a bucket of cold water on me and tell me that I could buy these 4 units for $500,000 and lose all my equity when the land lease expires in 2052, OR I could be sensible and put my time and money into something that has a 1% return AND that will have "guaranteed equity" when everything is all said and done?

Guaranteed interest of 4%, non-guaranteed dividends hovering around 5-6%, Living benefits (because what if you don’t die, but your terminally, critically, or chronically ill?)

Does anyone have experience in enforcing a personal guarantee on a commercial lease default? 

In a large multifamily, you'll need a partner who can sponsor your debt.For a small conventional property, you'll need to tag team with a friend or family member who can guarantee the debt.Partners are your way to go ...Unless you can talk the seller into financing the deal.

But I can pretty much guarantee you that investing the 100k cash in hand will result in much larger profits than the 210K we are talking about after 15 years.

Try to get the best guarantee and credit that you can if possible.Restaurant is a tough business.