10 years ago I worked for a startup that wanted to exactly the same. Basically it was a toolbox where you could add things such as a map, an image gallery, texts, documents. It was back in the days where everyone wanted to have an app even if they didn't needed. For example restaurants. The project failed, it was just way too complicated, both for the end user and the development of the project itself. Also a lot of stuff was faked. When some one would order the App, it would still be "Compiled" by a developer and "compiling" meant basically coding what the customer had ordered within 2 days.

Anyway, at least in their case you had access to the final source code.

EDIT: I just wanted to add that you are probably far better of if you hire a random guy from India on Fiverr to the app for you.