@PUNKEY,
It is quite common here with charities/non-profit organisations.
More than 50 years ago, school friends did it regularly: it was the cheapest method to go to a foreign country, meet new foreign friends, see a lot and do some charity as well for a low price. (That were camps for building and renovating council houses, youth centres, etc)
Today, their are even more possible
work camps than when I was young.
Internships (= working when at university on a subject you study) are paid, however, often just with "pocket money", some large firms pay nothing.