You have found a wonderful house you'd like to swap with during the summer.
Send an email to the owner of the house (contact person).
Write:
who you are;
that you read his / her advertisement on the site;
who you will be travelling with;
what you like about his / her house;
what kind of house you have (location, attractions near your house, number of rooms, names of rooms).
Look at the descriptions on www.lovehomeswap.com if you need inspiration;
when you want to swap homes;
that you look forward to hearing from him / her soon.
Tips:
Do you think this email should be formal, neutral or informal?
Be consistent with formal, informal or neutral language in your email!
Have a look at the toolbox (reference, words) or the warming up section for help.