I just made a big purchase so I have about 300k in my whole account right now. As of writing, I have nothing in my bank and nothing in my tills.
Sarah says I'm too rich but Sagittarius says I'm too poor so I can't view either one.
I believe the cut off is 1.5mill so with 300k, I should be allowed to do her quests.
I had this issue before because I had sP offered in trades, which is counted.