The biggest instant homebuyers — Opendoor, Zillow, Offerpad and Redfin —  stopped making purchases in March, in some cases backing out of deals and forfeiting their deposits. Now, some iBuyers are coming back, but they’ll need to prove the model can survive a downturn. Marketplace’s Amy Scott speaks with Mike DelPrete, who watches iBuying closely. He’s a scholar-in-residence at the Leeds School of Business at the University of Colorado Boulder.