There was at least one company selling this sort of thing as a product back then. It was more efficient than conventional electric heating, if I'm not mistaken, even without the income from mining.

There's a space heater called the Trio and a few furnace replacement things. And in general, waste server heat can often directly plug into central heating systems, be it mining bitcoins or Google datacenters.

Move into a cold climate, and buy a house that has only electric heaters. Those were popular in the 70s, and nobody wants them now, so you can buy one with pocket change. Build a mining cluster in one bedroom and install air ducts to distribute the warm air throughout the rest of the house.