In?

you're breaking up a locution: "done in" means killed, obliterated, destroyed, ruined--hence, "Slumping career and income might be done in by . . . " could read as "Slumping career and income might be destroyed by . . . "

That's what I was going to say, Setanta.

Ah, thanks. I should have found out the phrase in my dictionary (of course now I found it out -- because of your correction.)