@Alberto Nikodimov
Can you clarify your previous relationship with the investor? It looks like you said he invested through you as you being the agent, is that it, or did he loan you money for your own rehabs? Makes a big difference on who needs who. Did he have full ownership before and he is offering to bring you on as an equity partner - if so, he is doing you a favor.
50/50 is fair, or 60/40 to the investor as a general rule. However, if you are 10% of the investor you would get 10% of the investor profits/equity, and sometimes would still get the commission when buying/selling.
I disagree with most posts above. Investors and workers need each other. If you didn’t need the investor you could borrow money from a bank in the 3-4% range now and keep the equity for yourself. If he had enough people to find deals he would just pay someone commission and finders fee and a rehab/management fee. Everyone sees it from their own perspective and how important they are in the services or cash they bring, but a lot of people - especially starting out need to partner to grow and it’s mutually beneficial.
Part to have part of a whole pie then none at all...