Is there a money cheat for Fallout New Vegas?

There are, but only for PC. The "~" button opens up the console, for which their are dozens of commands. google fallout New Vegas Console commands for a list.

A few quick good ones

tgm: Toggle god mode; Infinite health, never reload

player.additem f (#): where (#) is the number of caps to add

tcl: toggle clipping, or walk through walls