The fastest-growing segment of the housing market today is single-family rentals – specifically detached homes or townhomes, according the Urban Institute. The shift to single-family rentals is being driven by a number of factors, notably tight mortgage credit and millennials’ lifestyle choices, which differ from earlier generations’.Single-family rentals (one-unit, attached and detached) make up 35% of the nation’s 44 million rental units – up from 31% in 2006. More than half of renters live in structures with less than four units, according to the Urban Institute’s Sarah Strochak. And growth of single-family rentals has outpaced growth of both multifamily and single-family owner in recent years. For the past three years, single-family rental has hovered around a 30% growth rate, compared with an average growth rate of less than 15% for multifamily during the same period, Strochak wrote for the Urban Institute.