Emmanuel,
You should be able to check his real estate license with the state to make sure he is who he says he is. I've been jerked around by as may licensed folks as non license folks over the past 15 years but if he is licensed by the state then you have a mechanism for seeking redress outside of court should things go south.
I hope he is using some type of legal entity to purchase these properties such as an LLC rather than a general partnership. This is not a necessity for some but it is something i would require before joining the group. Assuming so, you should be able to confirm with the state that this entity is in good graces with the state but that will not tell you if it is a good deal just that he is current with the paperwork.
You should be able to check county records (maybe even online) to make sure the properties he claims to own are actually owned by the entity(ies) he claims owns them in.
Make sure you read and understand the operating agreement and how he is compensated from the get go. If you don't understand something, especially if it sounds fishy or shady to you, seek council or walk away. If he is bringing the knowledge, the experience, the labor, and the property then he needs to be compensated but make sure it is reasonable to you and clearly defined in the agreement. Good fences make good neighbors.
I've been involved in several partnerships of this sort since 2002 and thus far all have worked out well. Most of them I have been the managing member of but others I have been a passive investor only. In all three instances where I was not the managing member, I had a great deal of trust in the managing members in advance of the deal. It's always good to network with others who have achieved the success you are looking for well in advance of a deal.
My advice is to start small, learn as much as you possibly can about the process, and if I were you I wouldn't cosign the note but that's just how I like to operate when i'm a minority owner in any partnership that I don't control.
Please note that I am not an attorney or CPA. I'm just a gold old boy from Guymon Oklahoma and do not provide tax or legal advice.
Final thought, unless you need to flip to make money to fund the next deal why sell at all? I have found a market that I believe in and don't plan to sell anything else if i can keep from it. I did sell one place a couple years back where I made really good money but I often regret having turned loose of that property when I could have found other ways to continue growing without that big hit of capital.
I wish you great success in all your endeavors and look forward to learning what you choose to do?
