Geez, if you are asking this because the person or people building this don't know the answer, you don't have a technical team capable of launching your "thing" ASAP.

This is such a basic technical question that you need to stop what you're doing and find a competent technical co-founder before pursuing this idea any further.

Your app should include a login that would validate with your servers who is/isn't an active member.

Let's hop on a quick call and we can discuss specifics.

Just so you know, Apple rarely approves apps for subscription billing so you will likely have to build your own billing backend.

If you are in the mid of app development then I assume you had already shared this with your tech team. If they were unable to answer that then you are surely in trouble. Fire them right now! because you don't even know what they will end up building.You might end up getting a rejection from Apple store if the app is not "wired" properly.

On the other note Apple doesn't have any problem with subscription based apps, they have problem with the nature of the app. With recent updates they have provided support with there SDK but have gone very strict with the privacy policy in respect to the end user. Otherwise the billing is through the same old app store billing system (70% dev/ 30% store).

Hope it helps.

Subscription-based apps tend to see higher revenue per user than apps with other business models. Subscription-based apps offer a genuinely nice, steady source of reliable income, especially compared to other app revenue models. This trust in your revenue flow allows apps to be more confident in their marketing efforts and in planning major feature upgrades that can be developed without constant fear of things collapsing. Mobile apps relying on subscriptions also have the bonus of even more predictable, reliable income by offering discounts for longer subscription periods. Many apps will offer discounts for users who commit to 6- or 12-month subscriptions. Being able to offer discounted subscriptions also offers apps some unique retention options. The subscription app model also provides a higher likelihood of an engaged audience. Maintaining app engagement is a huge challenge for many apps, but it tends to be easier for subscription apps since users are more actively invested in making sure they get as much out of your app as they can. Of course, it is your job to foster that engagement and make sure that users have interesting, rewarding experiences each time they choose to engage with your app. Since users are paying you a monthly, recurring fee, they will expect more than they would for a one-off app payment. When you are asking your users to pay you each month for access to your app, you are really obligated to continuously provide new content and/or features for your user. Personalization can help a ton with keeping users happy and satisfied with your app’s value – keep tabs on what kinds of content or which features an individual user frequents the most, then make sure to send a push notification and email when you launch updates that will connect with their specific interests. Users need to be properly onboarded to understand the true value of your app. Most users will need temporary access to your premium content to be convinced of subscription on a per month basis. All apps do this differently – for some, the first week or even month is free. Spotify offers their premium service for 99 cents for the first month.
Figuring out the precise amount of time users need to get won over by your service can be tough. With other apps, certain features can be used for free indefinitely, but the higher value benefits being for the paying customers. Launching your app with a subscription-based revenue model is one thing but transitioning from a one-time fee to a monthly charge can result in some serious backlash from existing users. What is crazy is that Zombies, Run took great care of their existing players, who received all content and features developed up to that point in time for free, plus a discounted subscription option for future content. When making a transition from a single fee to a subscription app model, make sure to be clear with customers and treat them well.
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath