By Dan Weil A relief from the rise in mortgage rates: The 30-year fixed mortgage averaged 4.99% last week. Finally, some good news on the housing front for buyers … well, sort of. Home inventories, as measured by active listings, soared at a record-high year-on-year rate of 31% in July, according to Realtor.com. That marks the third straight all-time monthly peak. The good news is this means more homes from which prospective buyers can choose. The bad news? It reflects the unaffordability of homes for many would-be buyers. “The U.S. housing market continues to move toward more evenly balanced …