Hi Ed. I am not sure about a "going rate" for deferred payments but there are several leagl issues that come into play (as I assume these rates will be agreed upon in a contract of some kind) on the payment (money) side of our business. For full disclosure, I am not a lawyer of any type or even pretend to be one, what I am about to share is just what I have learned from books and discussions with others (though that whole disclosure thing did feel kind of lawyery, didn't it?)
As far as rates go you have to consider what kind of actors you are using, are they pros who are SAG members? If that's the case then I understand that there are certain base rates that you may be required to factor into your budget (even at SAGIndie rates). If they are just your buddies, or local actors not affilaited with any type of union or organization then I would presume that what you want to share on the backend (i.e., if money is made or expected to be made) is part of the negotiation process of the contract. How these contracts are enforced becomes a matter of law (of the country or state that you are working in). You may seriously want to consider engaging the advise of an Entertainment attorney or read up on these types of things before you go signing contracts (even with friends and especially with family).
Even the word "deferred payment" raised a legal flag in my mind. In the US, each state has it's rules when it comes to deferring payment (once again talk to a lawyer or read up on this for your applicable state). My understanding is, because of the past abuse of payment structures in our industry laws have been set in place that prevent you from just deferring payments. Based on the kind of business entity you set up as your production company (i.e., not-for-profit, sole propritorship, LLP, or corporation) you may or may not be allowed to defer payments.
The theme of my babble is this...talk to a lawyer or read up on this stuff. We have such a passion for movies that it's easy to forget that ours is an industry that is exposed to so much legal stuff that it's crazy. Things like missing a simple release form can kill an entire project. But we are artist who just want to create and not get bogged down with the business or legal side of things. In bigger productions they have time, money and people for that kind of stuff. For us low/no budget folk we have to wear many hats. We have to be deligent and know a little bit about a lot so that nothing gets in the way of completing our work.