Almost anywhere in the world you want to go, you can likely do it through WWOOFing. Over 60 countries have their own WWOOF organizations, but there are many countries that have hosts and no official organization as well.
The work you do covers not only the cost of accommodations, but food as well (in most cases). Being that the work is done on organic farm, it's often nutritious and high quality food (depends entirely on the individual host).
Over 60 countries have their own WWOOF organizations, which each have their own individual membership fees. If you want to contact a host in a certain country, you first have to pay the fee for that organization. If you play to travel around and work in a variety of countries, the membership fees can add up.
The jobs that you'll be doing vary greatly between hosts, so you're able to find something that suits your interests and skills. They range from helping in guest houses to painting houses and gardening (lots more, you can search them here.
Workaway suggests 5 hour work days for working off food and accommodations. However this is just guide, you can adjust this arrangement with your host. However, there is nothing protecting you from your host asking for more hours once you get to the destination. This is a pretty frequent occurrence, and limits the time that you get to spend exploring your destination.
The amount of work depends on the animals you'll be looking after. Generally, you'll get the majority of your time to do as you'd like around the area.