Possible new clent

I just got a call from a possible client that i have been courting for years. He has screwed me over before with his indecisiveness. I know I don't have time to take on a new client. But thats just temporary. Once I'm over this hurdle if I don't take him I might regret it. But this again he might try and screw me again which will had to my stress.
He wants me to "consult" for now. Not sure what to charge him. Hourly I guess. When I teach I make $35./hr. When I bill my clients I make a % of what I earn for them. This is usually very good deal. But this guy... I don't know. I don't know if I trust him. If things worked out for us it could be very good for my business. He knows a lot of dr. in the area. Which I need to be in good with.
I had to end things badly with a couple of drs. who tried to ruin my good name. Lucky for me this did not hurt me with my clients I already had and I even got a very good client in the city near me. But it would be nice to have some locals.
Any thoughts are welcomed.