TALK TO A LAWYER. They will guide you through these questions. Do not cheap out on the lawyer now, you are asking important questions that will fundamentally affect the ability of your business to succeed. These are common questions and a lawyer will work it out.
If I were the OP I would do as he/she has done and ask questions of other entrepreneurs first. For the record, I agree with aditya that vesting is the main technical answer here. Maybe you'll get lucky and grellas will chime in!
i guess my question is generated by my anxiety about having a long term agreement but not having distinct divisions of power. if anyone has done it before and lived to tell could chime in that would be awesome!!!
Either there's something about your partner that's bothering you -- in which case you should address it explicitly and not put it off -- or you might be bringing worries about power, conflict, etc., into this situation that actually originate elsewhere, in which case you should get aware of that and make sure it doesn't poison your relationship. Either way, the technical legal level is probably the wrong way to approach this. If you can't trust each other, no document is going to save your business.