Rising mortgage rates and a shortage of newly built single-family homes have made the dream of owning a small, affordable home unattainable for renters who would like to make the move to homeownership. After the latest mortgage rate hike, renters in 46 of the 50 largest U.S. cities can no longer afford a starter home, up from 44 just two months ago, according to a new report from Point2 released this week.