Most Helpful Guy
You should lay it all out BEFORE moving in, if that is what you end up doing. Just say what you said here -- the jealousy factor, the boundaries concern, the prospect of another man even while still coping with the jealousy factor, and so on.
Remember though, even if you communicate it, this will be a relationship based on using one another. Using him for low rent is a perk, but its still using him. Well, all is fair in love and war they say - people use each other all the time. The problem is, if the rent goes up or something he is using you for dries up, the deal could be off. Your living with him would be so tightly linked to mutable circumstances that you are looking at a house of cards for a foundation.
I'm not saying you should or shouldn't take it, but if you do, don't let yourself get surprised if the whole thing bombs out on you -- or at least make a contigency plan.