That's great news that you have found a house sitting assignment!
Please find below a link to our house sitting agreement. Generally, our advice is that you should meet with the home owner first before agreeing to the assignment. During this meeting, you should go through the house sitting agreement with them, so that your (and their) expectations are met and agreed upon.
If you are coming from overseas and is unable to meet with them, you can arrange to meet online (eg. Skype) although this may be a bit harder.