Creating an app for iOS can be a real pain. While the technical challenge level of creating an app this way may be low, the overall flexibility and room for error is very low as well. You really cannot create anything very unique or special with a free app that you download from the internet. The feature set is limited as well. If you want to stretch your app over time, your app will limit you. But if you do not stretch your app, then your app will not scale. And you could end up having a bad product.
So you need to decide whether or not you want to use iPhone development tools to create your app or if you need to build it yourself. There are pros and cons to both methods. The key is to make sure that you are comfortable with the programming language that you are using for your app. IPhone applications need to be easy to write and understand so that they can be used by people with no previous experience. If you use a non-proprietary programming language, then you will have a higher likelihood of the user having issues with your app as he uses it.
I recommend looking for an iPhone application development company to help you develop your app. They can handle the coding and design the app in the same package. Then you can focus on marketing and other aspects of your app. If you are not comfortable with developing and marketing your own apps, then you should consider hiring a professional. You will still get a high quality app, but you will also have a strong foundation that can grow and change over time.