I am not sure what your energy rates are where you are at, but the electric heat is pretty innexpensive to install, and has virtually zero maintenence costs. Up where I live, electricity is too expensive to heat with on a regular basis.

How about propane or natural gas radiant style heaters? They might be a bit more to install, but could provide you with a good source of heat at a reasonable price. They also do not require a huge amount of maintenence.

Other than that, a small oil furnace (a ceiling mount type) could work, but I would tend to look at the natural or propane first, for the ease of maintenence. Some of the radiant type don't even require electricity to be installed, or venting. You just hang them, and run a gas line to them. Others might require a vent through the wall, but again not too bad.