Cost of living(rent, utilities, data/wifi, groceries) is $500 USD per month for most countries, up to $1000 for most others.
Health care and insurance abroad are both pennies on the US dollar for the highest quality of medical care
You usually don't need them; when necessary, visas are almost all entirely online: a fifteen minute e-form and nominal fee offset in your first day by the drastically lower cost of living abroad.
Any job that nets you $500+ a month works. There are almost 2 billion English students globally right now, so native English speakers have lucked into a guaranteed job on or offline.
Some countries and schools require a TEFL certificate or prefer candidates with an associate's degree depending on the position, but if you want to teach English, all you need is to be a fluent English speaker.
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jobs are full-time or part-time, 1500-2500 USD equivalent a month depending on hours, in Spain no degree or TEFL certificate is federally required, although the TEFL certificate is highly recommended and worth the week or two it takes to become accredited.
I assume you'd need to speak Spanish, though?
english schools only want you speaking english in the classroom, and they'll have school assistants nearby, often in the classroom, to help you out when Spanish may be necessary, either for you or a student.