I have an older (2003) Citation Supreme. 10' 4". Single slide.
Fully insulated with double pane windows. Used it in below freezing weather. If we have a plug in we have a small 1200W electric heater. (Home Depot $20) Otherwise the propane furnace works well. I upgraded the thermostat for better control.
The insulation also 'works' in the summer to keep the heat out.
The interior volume is so small it take very little energy to keep it warm inside.
Citations were a casualty of the last recession but there are a lot of them for sale. I use Auto Trader, and of course craigslist and kijiji. General Coach also made many similar TCs under different names.
