Not sure why you are getting down voted. It's true, house size has inflated significantly, and it drives cost. My first home was built in the 1970s and was 1500 sqft, bought for $136k in 2017 (Zestimate is about $200k now). My current one is about 3000 sqft and it's stupidly big, but it's what was available that's not a total fixer upper.
I saw an article in WaPo the other day about house size and affordability, with one couple having a baby on the way and deciding not to move despite "needing" more space. Their house was crammed to the gills with stuff. So. Much. Stuff. I think removal of a lot of the stuff would help free up living space (so did the WaPo commenters).
I've never done a thermos on a hike, although maybe I will start for winter. I would recommend a cup to drink out of, because otherwise you run the possibility of burning yourself on too-hot liquid. However, if you already have an insulated cup, you could get away with a simpler thermos.
How much volume do you want? How long do you want it to be warm? What is the use case (liquid only, or chunky soup)? A travel coffee container might be sufficient.