Craig it sounds like the house is almost yours, congratulations! Heat pumps cost the highest initially and use electricity but are less expensive to run in everyday use. Gas heater are cheaper but are more expensive to run if used everyday.
I use a gas Sta-rite, mainly because ours is a small indoor built in pool spa that we only use a couple times a month. Get a good pool cover, as that will also save you money on the heating expenses.

A computer once beat me at chess, but it was no match for me at kick boxing.