What would you ask in return...?

If a woman asked me that, I probably would never go out with her again, or at the very least, I wouldn't consider her a serious relationship possibility - basically I'd take the way she asked that as having ual undertones, and a woman whose life can be purchased via a date is no woman I want any part of. At least not for a serious relationship. Asking me that would set off a huge red flag, and basically, from that point on, she'd be a girl who I would see for fun until something serious comes along. I wouldn't feel guilty about that because I'm treating her exactly as she seemingly wants to be treated. Of course, there's the possibility that she was just goofing around, but I'd definitely be a bit less serious about the whole thing until she proved me wrong.