I know nothing personally about this but a travel blog I read just posted this. (it's the guy that lives in a veggie powered truck with a large family )DiscoverShareInspire.com
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Looking for a free place to live in Guatemala for 4-6 months? Poco a Poco is looking for a volunteer couple/family to live and teach at their project on the shores of Lake Izabel... message me if you're interested!
Here's their website
http://pocoapoco.gogivegood.org/