(Save the date: RealShare New York comes to the Grand Hyatt, New York, NY, October 9.)

NEW YORK CITY-The single-family home market is beginning to show signs of improvement as inventory continues to drop, mortgage rates remain low and affordability stay at an all-time high. The latest S&P/Case-Shiller indices for the month of April show that average home prices increased 1.3% for both the 10- and 20- composite – and while one month does not make a trend, the combination of rising positive monthly index levels and improving annual returns is a sign that the residential market is stabilizing.

“It’s very encouraging news that home prices are now beginning to show slight positive upticks from a year ago,” Lawrence Yun, chief economist and senior vice president of research at the National Association of Realtors, tells GlobeSt.com, noting the recent months increases mean that year-over-year gains were overall positive. “Looking at the three-month average of February, March and April, and since that time, the inventory condition has tightened more, there are more buyers in the market and based on the normal supply and demand dynamics, it would imply that the prices are firming up even more at this moment in late June as we move into July.”

S&P Case Shiller, which is calculated quarterly based on a value-weighted average, show that April’s data indicate that on an annual basis home prices fell by 2.2% across 10 US cities and by 1.9% for the 20-city composite versus the previous year. While still negative, the numbers show an improvement over the annual rates of -2.9% and -2.6% recorded last month in March.

While spring and early summer tend to be the most active buying months, other factors are also bringing people back to the market, such as rising rental rates and increased home affordability. “What people are looking at is two things: what are my month-to-month costs in terms of owning versus renting and then what I look at a house price to do if they do go ahead and buy that asset,” Gary Painter, director of research with the University of Southern California Lusk Center for Real Estate, tells GlobeSt.com. “For a long time, people were very concerned about buying a home for the first time because it has just gone down. But now, people are feeling a little more confident because house prices will be flat for a little while, so then it becomes a decision of ‘what I am paying in rent?’ versus home-owning after accounting for taxes and insurance and the amount of money that I need for a down payment. You are definitely seeing a piece of the rental market looking at owning their first home again. There has been a delayed entry as an independent household because of the recession, so the overall rental market will be pretty vibrant for a while and prices will continue to go up.”

However, qualifying for a mortgage is still a challenge for many. Data from USC shows that in 85% of markets, it is better to own than rent, but at the same time, four million homes in the US have upside down mortgages.  “Given that we have historically low mortgage rates, for those people who are able to qualify and obtain a mortgage, it is not necessarily an easy thing to do,” Yun says. “But there will be more people seeking ownership alternatives instead of facing the higher rent year after year.”

NAR, unlike Case Shiller, measures the median price of homes being sold instead of the repeat sale methodology used by S&P. In its most recent findings, NAR found that total existing home sales, including single-family, townhomes, condos and co-ops, declined 1.5% to a seasonally adjusted annual rate of 4.55 million in May from 4.62 in April, but are 9.6% above the 4.15 million-unit pace in May 2011.

“Right now, there are fewer lower price homes getting sold and more upper-end price homes getting sold, and as a result, it skews the median price upward, but it does not necessarily effect homeowners price appreciation,” Yun says. “But the NAR data advantage is that it is much more timely and generally you even though have that drawback, it tends to be a good indicator about Case Shiller may happen in the future.”

Locally, home sales have remained strong. Michael Slattery, senior vice president of the Real Estate Board of New York, says citywide home sales went up to 9,033 in the first quarter of 2012, compared to 7,796 in Q4 2011 and 8,999 in Q1 2011.  “The housing market is improving, and it seems to be pretty much across the board and moving in a generally positive direction,” he says. “To the extent that it is showing improvement, I think that [Case-Shiller] is an accurate reflection of what we are seeing.”

But Painter says the real estate community needs to watch if the increases are truly a trend or not. “If we see three months in a row where house prices are ticking upward, that’s where I will start to be excited,” he says. “Looking month to month, you can have a dip, you can have an increase just based on the actual sample of houses that transacted that period.  You could have just happened to have a representation of distressed properties one period and all of a sudden you’ll see a tick down, but it actually could be good news because investors are deciding to dispose the properties and things are getting better. My reaction is that it is a good sign, but let’s give it three to five months before we declare it a trend.”