There are several reasons one might want to setup a non-profit for this: - we can pool resources (money, but also technical expertise, availability to reply to abuse mails, access to legal expertise ...); - it gives you greater (but still not great) media visibility for advocacy/outreach and running donation campaigns; - it puts you on better footing if/when contacted by law enforcement agencies; - it makes it easier to find networks that aren't heavily represented in the Tor network yet, and are willing to host exit nodes.
Full disclaimer: I am on the board of directors and sysadmin team of Nos oignons [NO], a French non-profit that operates Tor exit nodes.
[NO]: https://nos-oignons.net
Speaking from experience, DigitalOcean and Vultr seem to be cool with relays.
Also, occasional upgrades.