I'm curious if there is anywhere in the US that cheap that you can actually make more than $35-40k/year (locally, remote work is obviously different).

The median income for a man with a Bachelor's degree in the US is ~$51k [0] - which means a full half of reasonably well educated men make less than that (the numbers for college educated women are much more grim). I'm assuming there is substantial overlap between less expensive places to live and people making below median income.

[0] https://en.wikipedia.org/wiki/Household_income_in_the_United...

Location, location, location, even within the same city it's $300 to $5000 per month.