NEW YORK (AP) -- Wall Street gave up a sizable gain and was fluctuating Monday as investors speculated that the worst housing slump in a quarter century might be nearing a bottom, a trend that could be the catalyst to revive the badly beaten financial sector.

Investors, while still wary of recession, grew hopeful after the National Association of Realtors reported existing homes fell less than forecast. Some experts interpreted this as a housing market on the verge of bottoming out with a rebound expected to start toward the end of this year.

Wall Street also found encouragement after Visa said it still planned to go ahead with a $19 billion initial public offering this year that could go down as the biggest in U.S. history. Further, investors remained hopeful that troubled bond insurer Ambac Financial Group Inc. would receive a cash injection to help preserve its coveted "AAA" rating.

"The home sales, even though they were weak, showed some signs of stabilization," said Chris Johnson, president of Johnson Research Group. "People will get very excited if they sense a bottom in the financials because they've been the Achilles' heel of this market."

However, he warned that the market still remains highly volatile -- and that the Dow Jones industrials can fluctuate back and forth into positive territory several times during a session. The market this year has been prone to quick swings as investors buy on dips and then quickly cash out.

In midday trading, the Dow rose 13.27, or 0.11 percent, to 12,394.27. The blue chip index had been up more than 100 points earlier in the session.

Broader stock indexes were mostly flat. The Standard & Poor's 500 index shed 0.68, or 0.05 percent, to 1,352.43; and the Nasdaq composite index fell 1.65 or 0.07 percent, to 2,301.70.