@gray-scientist-12794 -- this app will be served from the app store? Correct?
In that case, both Google & Apple allow you to create subscriptions (for a 30% cut month on month). You cannot bypass this (especially on Apple) as far as I am aware.
For the web, you can use something like Stripe or RazorPay (depending on your geography).
You could also encourage users (though not explicitly -- else Apple rejects your app) to sign up using the web - saving you 30%
Good examples of this are Spotify. You can subscribe via Apple as well as on the web directly.