Apartment developer Equity Residential (EQR) reported funds from operations of $195.3 million in the first quarter, a 9% increase from a year earlier.

The Chicago real estate investment trust's FFO per share rose to 61 cents from 56 cents in the first quarter of 2011.

Equity Residential owns, develops and manages apartments. The firm took in about $141.8 million in the first quarter in income available to common shareholders, up from $123.9 million a year earlier.

FFO, however, represents a more accurate measure of a REIT's performance than net income.

Revenue for the quarter rose to $527.7 million from $466.4 million year-over-year, while expenses also rose to $381.5 million from $350.4 million.

"Fundamentals continue to be strong across all of our core markets,” said Chief Executive David Neithercut. “As we enter our primary leasing season, we continue to expect that we will achieve same store revenue growth for the year around the mid-point of our previously provided range of 5% to 6%.”

The company, founded by Sam Zell, also released more details on its effort to buy a stake in apartment developer Archstone.

During the first quarter, Equity Residential and the Archstone sellers agreed to a 60-day extension of this purchase right at an increased minimum price of $1.485 billion. On April 18, the parties agreed to an additional extension and increase in the minimum purchase price. Equity Residential now has the exclusive right, until May 21, to contract to purchase this remaining interest at a price equal to $1.5 billion or higher.

The bankruptcy estate of Lehman Brothers, which holds the remainder of Archstone, could match that offer, but Equity Residential would earn a breakup fee of up to $80 million. The company previously submitted a separate $1.33 billion bid for a separate 26.5% stake in Archstone, but was blocked by Lehman.

Equity Residential acquired three properties during the first quarter, totaling 3,544 apartment units and a purchase price of $159.1 million.