Joker would not last long in reality either, because he loses his superpowers.
Yes, Joker has superpowers, just like Batman and Ironman. They have the power of convenience. Things line up juuuuuust-right so that things work out perfectly. Like Batman having studied an ancient lost language juuuuuust in case he needs archaelogy to fight crime. Or Ironman making an anti-spiderman device in his spare time. Joker has the convenience of having all the guards looking the other way everytime he needs them too, and nobody with a gun in the room.
Joker would accomplish 1 high-profile crime, then the authorities would be all over him. It's not like he's not insanely rich with a a huge network of support like Osama. Joker would be toast pretty damn fast.