Volunteering fee in Costa Rica

Hello, I am Yukiko. I have been very interested in volunteering, especially helping children. I I am going to graduate from college in the US and I want to be a teacher in a developing country in the future. Before becoming a teacher, I want to get experience from volunteering. So, I am thinking about applying for volunteering for four months but a volunteer organization costs fee for volunteering, which goes to my living cost in a country where I volunteer. I paid for my tuition. I cannot afford volunteering fee, it is about $3500. This is bridge for my future. I really want to help children and get experimence for my future. I accept any amount even small amount. I appreciate you if you help me out. Thank you very much.  

-Yukiko