It really doesn't fit his schedule that he wants to play a thief, and he's struggling needing a bit of advice to get to even 2-1/2-2, what makes it so making a monk for sleeper will be so easy to just jump to that step that way? =/
Thief probably best to stick with wolf at that level. If very desperate for cash, aim for muka/desert wolf. Personally, just live by scraping by until lv 70 at least, as everything before that you really don't have much efficient method for farming. There's also the guide that's linked by Matrim to help you as well for general advice not specific to particular characters.
