@Stanley Blackman I really like the idea of partnering with a contractor. I recently partnered with my contractor on a flip, he is also one of my close friends and we trust each other, but it has been good because our interests are aligned.
One thing I would be cautious of in your situation is if you are only bringing $120k in land value and nothing else and he is bringing $800k to build the house and managing the build. It seems like he is bringing more capital and more work, so why is he giving you half the profit instead of just buying your land and keeping all the profit for himself?
Is he making a percentage of build cost like most general contractors do, so when he says $800k does that really mean $600k and he is getting paid $200k as the general contractor? I do really like the idea of partnering with a contractor but not as much if they are making money on the project outside of the profit share, that could be a conflict of interest.
What would happen if he went over budget and the house ends up costing what it's worth, do you sell and basically get nothing for your land?
What would happen if he ran out of money half way through the build?
I would have the conversation about these things beforehand so you are on the same page and then I'd write it all down so you are both in agreement.