You have had experience to know several things: 1) what you DON'T want to deal with, and 2) what you don't mind dealing with. Utilize your position as the BM/BO to craft a boarding contract that states clearly what you provide/rules/expectations of boarders (if any), etc! Then, screen your clients and use your "gut" when accepting them into your facility. Generally, if we get an icky feeling about a potential client, the feeling is there for a reason... and we are able to tactfully decline their request to board at our facility ("we are not currently taking new boarders, but thanks for your interest!"). To avoid "co-BM drama", if you don't financially need one, don't take one on!
I really hope your past experiences drive you to succeed and reach for your goals, and that they have served as a catalyst for you in defining how your facility will be run. Surely there will be trying days where your clients may drive you bonkers, or the horses kicked down a fence board, or whatever... but if you love the situation overall, you'll manage! Best of luck in your decision making process! Keep us posted!