I'm not sure, but probably a good idea to get some kind of agreement in writing. May want to register it to a lawyer - I don't know, never been in that situation, but you are right not to rely on someone's word.
I have created an iOS game that should be out very soon - Just waiting for apple to approve it.
Please have a look at the vid, let me know your thoughts, should be out in a matter of days - free to play.