[rrrrrrrrrrrryan]

This seems reasonable.

Go ahead and collect the payment info before giving them access to the free trial, let them use the thing for free for X days, then when the free trial is up, block their access and ask them whether or not they'd like to pay for the subscription. It could literally just be one big button that says "accept." Then ideally, ask them again before each recurring charge.

Some people here are proposing an absurd amount of friction - one highly upvoted post suggested that the app should require users to re-enter their payment info before every charge. What if this app is great? What if I actually want to give them my money? Making me type in my credit card info repeatedly is nightmarishly bad UX.

Reducing friction is a good thing, even here. The important bit is just getting the user's clear consent by making it opt-in instead of opt-out.