Many homebuilders went out of business after the housing crash, and that has led to a historic housing shortage. And now investors large and small are jockeying to snap up homes as the tight supply keeps pushing prices higher.

So big companies such as Redfin and Opendoor, countless individual speculators, real estate agents and some more predatory outfits have been contacting homeowners, just on the slim chance that they might be willing to sell to some random person calling on the phone.

“They have just gotten increasingly worse in the past six months, six or seven calls every day,” says Lauren Barber, who lives in Columbus, Ohio…

How much of this is legal or otherwise is complicated and can depend on local rules. The city of Philadelphia recently passed a law to crack down on the sketchier practices. It includes a local do-not-call list specifically designed to block cold calls from homebuyers.