It's difficult to give a time.  The matching process looks at your skills, experience and lifestyle with the needs and wishes of the service user.  It also takes into account the views and references of all the other people who live in your house, including other service users who are already living with you.  There are introductory periods where the service user would visit you, intially for an afternoon but then perhaps an overnight stay. There is no fixed pattern and it takes as long as it takes for everyone to come to a decision.