I've hosted 17 yo Chinese student 9 months of the year. 1099 show's monthly payment for food/trans. Can I list him as a dependent?

No. An unrelated person must live with you all year to qualify as a depdent. But see this:

https://ttlc.intuit.com/questions/1901071-can-i-take-a-deduction-for-housing-an-exchange-student

The link allows you to take a charitable deduction, but only if you are not reimbursed.  It is not applicable in this situation.

See this link:  https://ttlc.intuit.com/questions/1968512-we-were-just-told-that-our-stipend-for-hosting-an-exchange...

You can treat this income as self-employment income (business) as you provide substantial personal services....laundry, transportation, meals, cleaning, along with the room.

Expenses would be mileage, food, business use of home, (easiest would be to take square footage of room exclusively used for student using the simplified method)