In order to give expert app builders an idea of what's needed, is there a platform online or any helpful books that will aid in building an app that is user account based, will allow photos and details to be uploaded, combines social media concepts as tagging and notifications, and even mobile checkout features?
You should try Balsamiq for this. After this you might consider InVision for displaying working and designed solutions
Do you actually need a mock app, or just a wireframe/interactive design? It seems like you are trying to shop around to find a developer and they should be able to work from a design. A quick Google search reveals Pixate and Invision, either of which might do what you need.