Not much!!
The user and size limits are mostly indicators, and your instance won't be destroyed and you won't be overcharged if you go over them.
Usually that will simply lead us to talk about switching to another plan whenever you're comfortable with it.
If payment fails, nothing will be cut off either, we will eventually be in touch about updating your payment info, and if we don't hear back for 6 months we will consider shutting down the instance.
We currently support contributing to our OpenCollective account which should let you pay by credit card, PayPal, SEPA debit, Bancontact, and direct bank transfers.
If you have your own collective registered there, you may contact us to receive a recurring expense directly to your collective. Please contact us if you need anything else.
We do not offer any business class of managed hosting plans: you're welcome to subscribe to our services and donate generously accordingly to your means as a company, but be aware that this hosting service is still community-run, and has certain non-negotiable constraints :
We do not provide any dedicated hosting solution as of now.
Our members might be available for consulting work to accompany you in building such solution over an existing hosting platform that can follow your needs. In doubt, you're welcome to send an email.