I am a little late to the game and have been told several times throughout my adult life to invest in real estate, but I ignored the advice.

Certainly talk to your CPA or your 1031 QI, both of which should have had a 10 second explanation at the tip of their tongue.

Do we just have a written agreement between father-son (is there a viable legally recognized agreement online to use)?

Face-to-face connections can quickly build trust and often lead to referrals.2.Online Groups & Forums:Utilize Facebook groups, LinkedIn communities, and other local online networks dedicated to real estate investing.

What is the best way to handle it so that both LLC members have a skin in the game?

Just remember you are spending time and money to improve a space that isn't yours and you're not able to take the improvements when you leave, ownership should have some skin in the game especially in a new build.   

In online forums, the danger I've experienced is the "national" effect. 

It's the scam sales funnel 101 that you read about online with old ladies spending their last dime on some "guru".4.

Which they have no skin in the game (Technically).

Not us, and not the economists as it is all truly a guessing game.