I'm needing to install some kind of central heating system. live in California. Anyone know about how much it would cost to put in such a unit for a house about 1800 sq ft?

One contractor said that the heating ducts should be on the floor. But the house in question has only a crawl space underneath.

With forced air heating, does it really matter if the heating ducts are on the floor, wall or ceailing?

Do central heating systems also have some kind of cool air blower unit feature (not A/C) that would be good on hot days?