For the appartment dweller, I would buy a Kerosene room heater, like those at Home Depot. Read and understand the directions, and be sure to open a window so that the unit doesn't kill you by robbing the oxygen from the room. Propane could be used, but it is more dangerous than kerosene being under pressure, and the fact it could turn your apartment into a bomb.
If you plan to convert your natural gas boiler to propane, you will need a propane conversion kit for your burner, and for a non electric control, this mean a thermopile compatible burner set up. A thermo couple uses electricity supplied from the grid or some external source, while a thermopile generates a small amount of current from the heat generated from a pilot light. This setup would only work on steam heat systems, since hotwater heating requires a pump to circulate the water through the system.