Stop in for a cup of coffee

So question for the group, especially the northern group. I’m wanting to heat my little yard barn this winter, 12x28. I want something safe so I’m trying to stay away from el cheapo space heaters. But a permanent unit is way out of budget range for this idea. Anyone have any suggestions on a safe way to heat it?
Find a house trailer Miller gun furnace. It is tall but around 24"x24" set it on a thermostat. Around here you can buy them for $150 or a little more. I even heat my house with one.