iPhone Application

Hello, I'm looking to have an iPhone application developed, small and simple. The content is up to the author, but i would also like to be involved and have the final say in the decision.? If easier, i would also be interested in purchasing an already created application that has been submitted to the app store, or not.? This application will form a framework to which i can work with the developer to develop the application further over time and to also work on it myself.? As i mentioned this is only going to be a small simple application, but it need to be unique and capitulating. Another reason for this is i would like to keep the initial costs as low as possible, as i would like this to be an ongoing project.