Giving him the money as requested results in him walking away and refusing to give it to him results in him falling unconscious. No matter what happens, he doesn't become a lich, nor does he even become hostile and killing him results in reputation loss.
One possible exchange:
Hello guysh, how are youse doing. Heh heh, I kinda got losht on my way *hic* home. Any ways, thats don't matter no more, give me alls your moneys.
- 1:-Ah, look fella, we're not going to give you all of our money.
- Wrongs answer, boys. *hic* You shoulda givens me the moneys when I ahsked ya. Ya know what I am! I'll lets ya into a little shecret... I'm a LICH. Yessh I am, powerful magicsh I wields, and now you've made me mad. You've gots one last chancesh, give me alls your money *hic*!*
- 1:-Look, guy, we're not gonna give you any money. Now bug off.
- Whoa, ya guys jusht don't get it, do ya. I'm gonna killsh you with my alls mighty magical powers. So nows what's it gonna be, death or... or... or somethin'.
- 2:-We're leaving now. Bye.
- Hey! Whats are you, uhhh...
At this point he passes out and falls unconscious to the ground.