You simply need to know your own limits and limitations or even better your own preferences and priorities. If you genuinely know what you want and what is acceptable to you, you automatically know what is undesirable and unacceptable.

To some people sex for material (money, gifts, education or even food) is acceptable, to others it is not. It is their choice and hence their decision.

How does that require setting up borders between "you and the woman" as you put it?

Basic human respect for one another is absolutely sufficient, not to mention in a relationship where people hopefully are fond of each other.