Name you as a party of "additional interest" so you can monitor the policy to make sure it stays in force.

My biggest complaint is that I am more adventurous when it comes to the ideas and he has more conservative tastes - but it works out.

I probably would have left my money in the deal and taken the cashflow, or sold to a third party rather than accept the low offer from the partners, but that is me.

I agree and he and i have said we would do a contract to protect all parties involved.

I think most turnkey providers say they only sell in quality neighborhoods but I would love to confirm this by a third party.  

There are fiscally conservative BPers, believe it or not.

I haven't slept yet, so I forgot about the other party wanting to invest in your project, but my prior content is still relevant.

Again, not common overall, but if you do find someone, do thorough and careful due diligence.Finally I never recommend completely abdicating title research to a 3rd party, even a title company.

I'm not sure why you think it's the other party's job to "bring these things up in the beginning", and I am not sure why you didn't bring it up in the beginning, if that was a condition of your bid.  

There is another possibility that a third party known to the seller may intervene contesting the contract being predatory.