We talked about asking "Why" you need an app and hopefully you've got the answer. Next up is budget. Apps cost anywhere from $20K - $250K (and probably more depending on the dev shop). We haven't seen anything super impressive under the $20K mark, it's not impossible...we just haven't seen anyone selling the app as their main product in that price range. Unless you build it yourself - then awesome!
There are 3 components to consider before starting the development process:
Choose one, and then have a runner-up. There are folks that say you can choose two but it almost always leads to disappointment. If you choose features over quality and time, then you may end up with a feature full (overly complex), buggy product that takes longer than you expected. If you choose quality first, then know that feature prioritization becomes incredibly important - focus on the most important features first. Almost all teams struggle with this when they don't understand their customer or their business model.
Understand your customer, understand your business model and then proceed. This goes for enterprise apps as well - there is still an internal problem and customer. But what about "Lean" or MVPs? Definitely build a prototype, check out proto.io or Invision App, and use those tools before you engage a dev shop. The goal of the prototype should be to show people your idea, get feedback and narrow down the features that will go primetime in the first release.