The given answer is mostly bullshit. The real answer seems to be that Ellison's undiagnosed & untreated bipolar disorder had given him both severe depression (so he couldn't write anything new & salable, even if he was not yet bedridden) and worsened his compulsive shopping habit, so his finances were in freefall. Ellison had made a lot of money over the years... and spent it all. Over the next decade even his _Babylon 5_ sinecure from his friend JMS would run out and he'd approach rock bottom (culminating in a firearm suicide attempt):
"Impulse spending sprees are as textbook bipolar as the manic episodes that lead to them, and Harlan’s growing inability to make good decisions began to decimate his savings. Despite a precipitous drop in income in the years after _Babylon 5_, Harlan kept making high-priced impulse purchases of comics, artwork, and collectibles. Susan would tell him, repeatedly, “We don’t have the money.” But the cash went out anyway, leading to panic when the bills came in, often paid with loans from friends, followed by the same reckless spending and crippled decision-making when the financial dust cleared. “He can’t control himself”, Susan said. “I’ve had to hide the credit cards.”"
See JMS's "Ellison Exegesis" in _Last Dangerous Visions_ last year (which points out that 1997 would see the last original volume from Ellison ever, so 1998 is at the top of the slippery slope where his life really began falling apart from bipolar).