Be aware that not all A/C units are "heat strip ready" - even if the AC/fan selector knob seems to already have extra positions reserved for heating. I discovered my Coleman Mach A/C actually had the electrical terminals on the back of the sector switch cut off by the factory. They were physically there, but cut off flush with the switch surface, and totally unusable. Or maybe it was on the thermostat - one of the two. I can't remember the details - been too long - but the replacement part with all of its terminals was an unexpected additional cost.
I also prefer any old generic electric space heater. Much quieter than the A/C fan too.