-Maybe word got out that Luigi was "brave" enough to save his brother by eliminating every ghost in a haunted mansion,and they all thought that he could cleanse others just as easily.
-There could be relics,artifacts,etc. that Professor Elvin Gadd needs Luigi to find inside different mansions.
-E. Gadd could be looking for something that he knows has to be in one of a few different mansions.
Also,I thought of an idea for where a Luigi's Mansion could take place-in Coconut Mall,the course on Mario Kart Wii.You would have to eliminate the ghosts inside and outside the mall("outside" including:at other places like Daisy's Cruise Ship or Peach's Castle,or literally outside of the mall building.I finished LM2 Ideas long ago,I have all the ghosts,the story,etc.I'm glad there's a topic on this!
No,I don't want to buy MAGIC Beans! What are you,high?!
I read someone say somewhere (not in this topic) that Luigi DOES become a professional ghost hunter, but that doesnt seem to fit in with Luigis character (not that I really liked how nintendo depicted him after Luigis Mansion 1 and Superstar Saga), I mean, who would take up a job working with (or against) something they're terrified of?