Hi Brandon, just an idea:
Maybe when your users sign in to your app for the first time, you could show them a tab where you ask them to submit information (for their user profile for instance). As they submit the information, with an increment action, you could have a counter go up. Let’s say you want to limit your app to N free users. If counter <= N, then show xyz tabs (your app). If counter > N, then show a tab with instructions or CTA to become a paid user.