On the list, New York City ranks No. 1 and Columbus, OH ranks No. 10. The study compared vacancy rates, projected change in renter households through 2007, capitalization rates, average sales per units, and job growth. Denver's vacancy rate at 9.7% was the third hardest, topped only by Atlanta, ranked No. 2 and Charlotte, NC No. 8. Both Atlanta and Charlotte have vacancy rate of 9.9%, according to the report.

"Cap rates in the 5% to 6% area are probably as low as they can get and there is little to be gained by waiting during a period of rising interest rates," the report notes. "Next, most of these markets have fairly slow projected increases in the number of households through 2007. On top of that, apartment development has been quite robust even though vacancy has risen nationwide since 2000. For some markets, the timing looks right to take profits at what looks like a cyclical value peak."

The report goes on the note that most of the "seller-advantaged" markets are big cities. One reason is because there are barriers to entry in these cities. "Good high-rise apartment sites are expensive and comparatively scarce, compared to metro area where rental units are low-cost garden complexes at the periphery," according to the report.

The projected growth in apartment rentals in Denver is projected at 4.79% through 2007. Only Atlanta, the leader, at 9.08%, San Diego and Charlotte ranked higher. However, other cities are getting better returns for their multifamily building sales than Denver.. The average cap rate in Denver is 8%, the highest of the 10 cities. New York City had the lowest cap rate for apartment communities at 5.2%. The average price per unit sale in Denver is $74,786. Only three cities have lower sales per units: Atlanta, Charlotte and Columbus.

Job growth in Denver is projected at 0.4%. That bests San Jose, No. 3 on the list at negative 1.3%; Boston, No. 4, at negative 0.4; San Francisco, No. 6, at 0.1%; and Columbus, at 0.1%.