**I know this is a little long, but I appreciate any advice!**

A little background: I am 28, my husband is 30. We have been married for almost nine years, and have no children. In spite of our choice to (thus far) be childless, we are very close with our numerous nieces and nephews and love spending time with them. All of our extended family members live in small towns in Arizona, where we grew up. My hubby and I made a deliberate choice to leave the small town and experience bigger cities - we currently reside in Phoenix, AZ. We are now both college graduates (each of us is the first in our families), and are successful professionals.

The situation: Last weekend, my sister-in-law, her husband, and her five children (ages 5-17) came and stayed with us for a couple nights here in Phoenix. I was approached by the 17-year old girl, and informed that she was given quite a disgusting ultimatum by her parents. She's at the age where she is beginning to look into colleges, and was told that her only options were to either stay in the small town and go to the local community college, or leave the small town for a different school and be financially cut off. I confirmed the information with her parents, as I know that teenagers like to stretch the truth. It does seem as though her parents are possibly un-intentially holding her back. She is a VERY smart girl with a LOT of potential that shouldn't be wasted working at a pizza shop in a small town. (No offense to small towns... she just wants something different, as I did. I completely relate to her.)

She and I began searching out our local colleges online, and found that there are several very good options (some even fairly inexpensive) for her, if she were to move to Phoenix. Problem is, she can't afford to pay for the tuition on her own and room/board, etc. My husband and I discussed the matter and offered to have her move in with us. There is a community college less than a mile away, many opportunities for jobs, and she would be in a stable, trusted environment (we are close to her parents and know that they trust us to continue teaching her the things that they do, etc.).

The question (finally): I've never had a teenager live with me! I'm the youngest of only two children, and like I said, we have no kids - I rarely am even around kids and am frustrated by teenagers in general. I know this girl of course and she and I have a lot in common and I'm 100% comfortable with her (or we wouldn't have offered). However, how do I treat her like my niece rather than like a roommate? She will be 18, but I don't want to be the complete opposite of her parents and basically let her mooch off of us and contribute nothing; I also don't want to give her the impression that I'm trying to mother her.

I guess I'm just looking for some guidelines on how to treat her half like my child/niece that will have chores and contribute to the household and have a curfew, etc., and half like the 18-year-old college student she will be.

Any suggestions?

Thank you!!