Dear Roberto Inocencio,
Good day! Thank you for posting to Microsoft Community.
To answer your question "Does this mean we can use this and not have to worry about renewing cost as long as we put a valid payment method on our account and keep our non-profit account up to date?"
==>Yes, that is correct. Microsoft 365 Business Premium for nonprofits offers up to 10 free licenses for eligible organizations. As long as you have a valid payment method on your account and keep your nonprofit account up to date, you can continue to use the product without worrying about renewal costs for those licenses.
If you have any other question or need further clarification, please feel free to let me know,
Thank you for your precious time. Have a nice day.
Sincerely,
Libeamlak | Microsoft Community Moderator