Buying an electric heater upfront is inexpensive plus you don't have to
worry about venting issues, but operating costs will be expensive.

Gas heaters will be expensive upfront plus you will have to vent it to
the outside , but operating costs will be less than electric.

I had a gas wall furnace in my old condo that vented to the outside. It
did a pretty good job.
It was this one.
http://shoppingcart.msservicecompany...&itemid=sa25ng