Must need the money. But for what?
It appears from this information that he was never a U.S. Citizen.
"Cat Stevens was born Stephen Demetre Georgiou in 1948 to a Greek Cypriot father and a Swedish mother.
The family owned a restaurant on Shaftesbury Avenue, in the west End of London, and Stevens and his older brother and sister waited tables from an early age.
From 2006:
"Homeland Security officials said Yusuf Islam — formerly known as singer Cat Stevens — will be deported Wednesday after being denied entry to the U.S. Stevens had recently been placed on a government "no-fly" list after U.S. authorities received information indicating associations with potential terrorists, a government official said."
Cat Stevens to be deported after jet diversion
So what we are left with is that he is not a U.S. Citizen, and he has a prior deportation. Does it surprise anyone that the Obama Junta is allowing him to perform?