In November, existing home sales volume fell below year-ago levels for the first time in 29 months.

Sales volume was 4.96 million in 2012 and fell to a seasonally-adjusted pace of 4.9 million in 2013, according to The National Association of REALTORS®.

The NAR blames higher mortgage interest rates, constrained inventory and continuing tight credit, which may get worse in 2014.

Explains Lawrence Yun, NAR chief economist, "There is a pent-up demand for both rental and owner-occupied housing as household formation will inevitably burst out, but the bottleneck is in limited housing supply, due to the slow recovery in new home construction. As such, rents are rising at the fastest pace in five years, while annual home prices are rising at the highest rate in eight years."

Between October and November, sales volume dropped 4.3 percent.

The national median existing-home price for all housing types was $196,300 in November, up 9.4 percent from November 2012. But prices can't continue to rise if the number of transactions slows down.

Inventories are already higher than they were a year ago. In November, housing supplies were at 5.1 months on hand, up from 4.8 months on hand a year ago.

When housing supplies are under six months on hand, it's considered a buyer's market, but when supplies start to build, it's worth taking note.

Experts are looking ahead to January 2014 when the housing recovery could face new challenges - rising interest rates, stricter underwriting rules, and lower income-to-debt ratios for mortgages.