We hosted a student for a full year. A girl from Germany who had just turned 15 (younger than the average exchange student).
There was a short adjustment period, but it wound up being a wonderful experience. She fit into our family and we love her as if she were one of our own children. We still speak often and she has come back to visit us a few times (including a 3 week trip where her entire family came and stayed with us).
That said, I think we had a good experience because of the child we got. We did not have a good experience with the organization. We were asked to host less than two weeks before school started. (We only had a day or so to even consider it.) There was virtually no support throughout the year. The few things they did do, we (or the student) were expected to pay for and there were a few conflicts where she felt pressured from the director so DH and I had to intervene in her best interest. I probably wouldn't have been so bothered if I didn't learn that these kids paid around $8,000+ to the organization, and received virtually nothing in return (other than being assigned a host family).
What specifically did you find so expensive? Was it just another mouth to feed, or something else?
Our experience wasn't hugely expensive, but the expense is definitely something to consider.
Since we are a family of 5, I assumed that adding another child would increase our expenses by 1/5. However, for some things our expenses were drastically higher, often double. Things like... she ate a lot (sometimes just as much as all the rest of us put together) and she used more water than all of us put together. She also played sports and was involved in various activities, so gas was greatly increased. All things we were fine with, but I think it's worth potential host families to be aware of the costs involved.
Christmas gifts, birthday, going away party, dining out, and family activities can add up over the course of a year.
We also chose to travel a bit while she was with us because we wanted her to see as much as possible. (We lived in a very rural area.) Of course, we didn't have to do that but we were happy to and we all enjoyed the experiences-- going to the beach in Maine, NYC at Christmas (her first time meeting Santa), exploring caves, visiting historic sites, etc.