Mutants are a marginalized group in the Marvel Universe. As the next evolution of humanity, Homo Superior are feared and hated. However, that doesn't mean that there aren't some well to do mutants out there.
In fact, there are some mutants that even run multinational corporations. Groups like the Hellfire Club are run by mutants. Much of the wealth is inherited from their human forebears, but in the end none of that matters because it's in mutant hands. While none of them are Tony Stark rich, there are still some very wealthy mutants out there and this list is going to break them down.
That's right, Wolverine. Now, this has nothing to do with the Howlett family wealth of his long ago youth, but more what he's earned in the latter years of the 20th century. As a highly skilled soldier, Wolverine was under contract to multiple governments and probably made a good chunk of change over the years. This is a man who can take transcontinental flights to Japan at the drop of a hat. There's no way Wolverine doesn't have a sizable bank account with several secret ones from his years of black ops work.
If Wolverine has money from years of being a government black ops contractor, than there's no doubt that Mystique has more money. One of the world's foremost mercenaries, as well as a government employee (working with the Freedom Force and X-Factor), Mystique has earned a lot of money. Beyond her mercenary and assassin work, Mystique has also used her shapeshifting skills to grift countless people over the years out of their hard earned wealth. She probably has it squirreled away all over the world in bank accounts for everyone but Raven Darkholme.
Fantomex, before becoming an ally of the X-Men and later allowing Xavier's disincorporated mind to take over his body, was one of the premiere thieves in all of Europe. There was no art heist too large, no museum robbery too great, no artifact too haunted for him to go after.
Of course, much of his past was implanted into him by the Weapon Plus Program, but once he escaped, he made good on the personality they had created for him, using his considerable physical and mental abilities to rob his way across the continent.
7 Lila Cheney
Lila Cheney is an intergalactic rock star. With the ability to teleport anywhere, she's made a name for herself across the cosmos, playing on planets everywhere, from the Kree Empire to the Shi'Ar Imperium. While her wealth isn't all in dollars or any other kind of Earth money, she lives a life of abandon out in the stars. Her mutant abilities make it so she doesn't have to pay for transportation, meaning no expensive starship upkeep for her. She may not be a big name on Earth, but ask any Badoon, Skrull, or Cotati about her and they'll wax poetic about the last time she came to their world and entertained them. Her extragalactic bank accounts make the ones of human bands look paltry in comparison.
6 Emma Frost
Emma Frost, White Queen of the Hellfire Club, was born into a life of privilege... but it didn't last. Her family disowned her and she was forced to go out and fend for herself. Her life would have been much more difficult it wasn't for her telepathic powers. She got a job dancing at the Hellfire Club, where she used her immense mental powers to trick the patrons to get more money out of them.
Sebastian Shaw recognized her abilities and earned a place in the Inner Circle of the Club, a move that gave her access to more and more money. As White Queen, she earned a considerable amount of money and clout, becoming one of the wealthiest mutants around.
Roberto DaCosta, known by his superhero portmanteau Sunspot, was also born into a life of wealth and privilege like Emma Frost, but his family didn't disown him. Roberto was given all the advantages this kind of upbringing enabled him, including becoming a student at the Xavier Institute.
Even though he's spent most of his life as a superhero, he's also an astute businessman, growing the wealth he inherited to such an extent that he was able to buy the supervillain organization Advanced Idea Mechanics and turn them into an Avengers team that he bankrolled. Now, he's so rich that he can afford a space lawyer (see New Mutants #1).
4 Sebastian Shaw
Sebastian Shaw is the Black King of the Hellfire Club. This position allows him access to the wealthiest men in New York City, but Shaw already belongs among that number. Shaw was able to work his way up in the world, becoming a millionaire by the age of thirty with his company Shaw Industries. After joining the Hellfire Club, he was able to rise up the ranks and, with Emma Frost's help, takes over the Club.
Later, Shaw Industries bankrolls the Sentinel program, appearing to everyone to be an anti-mutant bigot. The amount of money it would take to do the AI research and build the massive machines would be colossal, but Shaw swings it easily.
Warren Worthington III, the mutant Archangel, was another mutant born into a wealthy family. The Worthington family is an old money family and Warren is a recipient of all that wealth. Warren is so rich, he's a legacy member of the Hellfire Club. Before his mutant powers manifested, he was a student at a prestigious New York private school, the Philips Exeter Academy, and is sent to the Xavier Institute after his wings start to develop. While tuition to the Xavier Institute has never been established, it can be inferred that the one he went to before was quite pricey.
Beyond that, he also bankrolled several superteams, including the original Champions and X-Force, paying for a massive base inside a mesa in the Arizona desert. Owning a corporation is one thing, but bankrolling superteams is next level wealthy.
2 Professor X
Professor Charles Xavier, surprise surprise, was born into a wealthy family as well and used his family money to travel around the world, learn, and then start a school for mutants. He was able to pay for the creation of all kinds of advanced technology and afford state of the art aircraft for his teams.
Recently, though, he took his wealth to the next level, investing in pharmaceutical companies and using them to distribute drugs created from Krakoan plants. The money he made doing this gave mutants economic opportunities they've never had before. Using the power this has given him, Xavier was able to get the UN to recognize Krakoa as its own nation, giving mutants something they've never had before- sovereignty in a home of their own.
While Xavier, as a head of state, has recently become ultra wealthy, there is still one mutant who has more money than him- Namor, the King of Atlantis.
While human royals are wealthy, they control a very small portion of Earth compared to Namor, who rules Atlantis and its surrounding undersea environs. Not only does that mean he controls a large cache of natural resources, but according to salvage laws, any sunken ship in his territory is his for the taking. Centuries of sunken treasure, undersea oil, all kinds of ores, and Atlantean advanced technology are all controlled by Namor making him the richest mutant by a wide margin.