Do many homes have existing hot water cylinders?

Is there a market for a hot water heat pump that can be retrofitted to just about any cylinder?

What sort of price would a end user be willing to pay for such a retrofit? (average sort of family). (apart from as little as possible!!!!!)

Do you get govt grants for these types of products ?(solar ect.)

What sort of gross profit do you contractors make on this type of appliance (domestic air con, heat pump)
cheers
Mad