Roofer is neighbors son, genuinely nice guy, want to trust him.

TRUST BUT VERIFY.

But from personal experience, I'd might do a land contract in which the seller becomes the bank for a time, until  you satisfy the contract, and the deed is held in escrow by a title company.Another scenario is to have the seller form an intervivos revocable trust, put the property into the trust, and assign certain beneficiary rights to you, along with a resignation of trustee (assuming the seller becomes his own trustee) and a quit-claim of any beneficiary interest to you, all of which is held in escrow by your title company.Remember, you and your neighbor can be as friendly now as front porch cousins, but when you throw real estate and money into the mix, ya never know how it might end up. 

Here's my opinion:I'd start with getting a deal structure on paper:1) Agree upfront how much value you assign to his land, and agree that your shared LLC/trust (or whatever you set up) will owe him that amount when you ultimately sell.

So most people on here are connecting on a business level, but also on a personal level.

If you are new to Crowdfunding, I wouldn’t recommend starting at the platform level.

The key for you is Develop trust early on and he may overlook your past inequities . 

They have already proved they cannot be trusted. 

The amount of my deposit is determined by the level of risk.

Obviously, you should consult with your CPA and lawyer (trust me, pay the fee, it's worth it).