As per title. I really hope it doesn’t get to this but with the energy crisis I figured this is probably relevant again.
Kmart and Big W have cheap options. Please leave some for the homeless! But if you’re really struggling tents can be had as cheaply as $13 with the next rank up being $39.
It goes without saying, please be careful about heating inside your tent. All of the warnings about fire hazards and carbon monoxide apply. Stay safe.
https://www.businessinsider.com/cold-korean-families-moving-tents-2013-1

Also, if you can have a pet, the warmth coming off their body can give you warmth and vice versa.
Yeah, the old saying ‘a three dog night’