Apps can be very technical to create at times and it is imperative for developers to outsource many tasks to produce an output within a given amount of time. If you are into building apps for passive income you can find many likeminded developers who can help for a fee online. Freelancing sites like Up Work are littered with developers from various countries who are very skilled. Creative sides of the game are sometimes hard to master so make sure you can draw out exactly what you want to achieve in a simple manner so anyone can understand your idea.
If you lack PHP knowledge for instance there is no need to fret you can always take advantage of those who are ready and able to help online. You can also leverage other things like blueprints. These are essentially templates you can find online for a particular set of code that can form the base to your app. If you have an app that is extremely creative then these templates might not be of much use to you.
If you have a complex game or even a simple one like Bus Simulator racing (Which you can download from the google play store), all you have to do is wireframe the game to make the entire creation process a piece of cake.
POP, Mock ability, Blueprint etc. are just some tools that will help you make your 1st wireframe. Make sure you read their documentation thoroughly to have an understanding of what exactly it does for you. These platforms all function very differently to one another.