Rebellious chicks seem pretty exploitable.  I'm chatting with one who desperately wants to get out from under her strict parents.  She wants to SB her way to earn enough to go off to college away from home, her parents won't help her do that. And not allowed to get a job. I don't think her plan is feasible, unfortunately, as her dorm alone would cost $8k.  She just turned 18 and can't really get out of the house much. So basically she'd have to skip school during the day to meet.  So it's highly unlikely I would risk meeting her.  But it's clear she would agree to just about anything sexual to raise funds.  She's already sent me nudes and vids.  And she's open to BDSM.   Cute face but she a big gal.  Probably middle-eastern. Another reason to avoid, who knows what sort of honor killing might follow discovery of their wayward daughter.

Even if she is legal (and if she is that close, you had better make sure of that), she isn't grown up enough emotionally to be a SB, escort, or even a too-young-GF. If she is using you to make a point to her parents, expect lots of drama. And you are right, she can't easily sleep her way through college away from home unless you are either very wealthy or very generous, which will create its own expectations.  

I met a gal like that once, but she was going to a very top-tier private college on the opposite coast from her family without relying on SB-ing for tuition and living expenses. She was super-smart and interesting and just escorting in reaction against a strict Catholic upbringing (all-girls high school, strict curfew, etc.) She had a lovely face and a slender figure with big boobs. It was fun talking to her over dinner and she was already a college junior then, so there was little risk of drama from her family or law enforcement. Even so, she wasn't worth the trouble.

Being 18 means she can consent. But that does not mean she can't be exploited. And being exploited generally tips the scales away from mutually beneficial to something where one of you wins and one of you loses.  Not a good basis for a healthy arrangement.  

 
If you want to proceed, I suggest you have transparent discussion to set clear boundaries:  regular but casual schedule, time apart is time APART, allowance is consistent and there will be no 3:00 am texts for emergencies. AND you will be seeing other SB's whenever you want to and she has no right to know about or ask about it.    

 
Keep her expectations low, and be honest & consistent. Then make a point of reevaluating frequently.  

 
Life is good

 
The Cat