One possible version:
Dear Mr. Smith,
I am writing to request the valuable chance to be one of the home-stay families for the American students. As an active girl studying in Guangming School of Tianjin, I’m quite good at English. My parents, who are kind and friendly, are in favor of my idea that I host an American student. We have a clean and comfortable house, which lies in a beautiful area of the city. Luckily, we have extra rooms for guests. My mother cooks well so the students will be able to enjoy delicious Chinese food. What’s more, my father is an excellent driver and we will be very glad to show foreign students around some local places of interest and some typical towns and villages in our area. I would greatly appreciate it if I could have the chance to make friends with them.
I’m looking forward to your early reply.
Yours sincerely,
Li Jin