Heat pumps have the same footprint as, and can replace, AC condensers. So if you already have central air, you should be able to retrofit a heat pump. You might need a new air handler, however.
Yes, that's true. I was just focused on another case of for example, trying to turn a large building's hot water boiler into an electrical / heat pump one. That is where the set of huge new condensers comes in, replacing like 1 previously dishwasher sized boiler.
If you don't already have central AC, you likely use window units. Mini-splits can be good in these situations. They can be mounted on the exterior wall and the heat pump can be mounted in many different places.