1. You don't need any extra coding for a channel that is a subscription or one-time purchase
2. If you want to have a free channel that a user can upgrade to a subscription or one-time purchase, then you will have to work with the code for triggering the upgrade, see roChannelStore in the SDK docs.
If you make a free channel into a paid channel, people who already have the channel installed for free will still have it for free, price increase only affects new users who install the app, so if you have 5000 users and you suddenly change the channel to a payed channel using our billing services, you won't get anything from those 5000 users, only the new users who install your channel, so you could wind up with 5001 users and only one paying user, so item #2. above is your best bet for avoiding that scenario.
- Joel