The 4.9% monthly gain was the fastest rise since August 2011, but the 4.89M pace is 5% lower than a year ago.
The NAR's Larry Yun notes slower price growth thanks to rising inventory along with a downtick in mortgage rates as boosting business.
Total housing inventory of 2.28M homes for sale is a 5.6 month supply at the current sales pace, down from 5.7 months in April, but 6% higher than a year ago.
The median home price of $213.4K is 5.1% higher than a year ago. Distressed home sales of 11% falls from 18%.
The percent of first-time homebuyers continues to disappoint, down to 27% in May from 29% in April and 29% a year before that.