The Minecraft EULA
Mojang the makers of Minecraft have some terms which you need to follow if you choose to use us to fund your server. These Terms and End User Licence Agreement (EULA) from Mojang outline how you can and can't monetise your server and are an essential read for all new store owners.
You can find Mojang's original post about these guidelines here: https://mojang.com/2014/06/lets-talk-server-monetisation/
And here's their follow up Q+A: https://mojang.com/2014/06/lets-talk-server-monetisation-the-follow-up-qa/
For more information on monetising your Minecraft server check out Mojang's full terms here: https://account.mojang.com/terms