system
Given the following post, respond as if you're commenting on Reddit:
human
[Marvel] Where did Xavier get the money to support the X-Men and the academy?

Xavier’s School for the Gifted is in a mansion with some very high-tech stuff, like the Danger Room, Cerebro, and the Blackbird and its hangar, plus a well-equipped team of super heroes. Where did all the money come from? Keeping something like the Danger Room and Cerebro up and running would surely require a lot of upkeep (which is often helped by Forge, but still) and power/electricity. And then there’s the actual process of building them. And then there’s the acquisition and upkeep of the Blackbird, as well as its hangar. Plus, there’s things like proper housing and food for students and faculty. Unless the school has an exorbitant tuition that most families would struggle to pay, there would have to be money coming in from somewhere.
gpt
Xavier came from a very wealthy family; at least one and maybe both of his parents were successful nuclear physicists involved with weapons research. It's also hinted that he may have had some backers in the federal government; in very early issues he has a phone line to an FBI agent named Fred Duncan, and that certainly explains how Prof got himself a jet from Lockheed, a company that normally only sells to the government (Agent Duncan incidentally resigned after a superior related to the Sentinel program ordered him to hand over any intel he had on the X-Men). 

At various times Xavier has also had financial backing from either Angel's dad, who is loaded. He also used to have a sugar mama who was princess of an entire galaxy.