If you have Freelancers that have common sell rates but individual buy rates then the "Prefer Buy Rate From User" can be the solution.
An example:
Object Class: Assistant Editor (no Activities) - Aimee is member; Sell Rate is 90 per hour
Object Class: Online Editor (many Activities) - Aimee is member; Sell Rate is 110 per hour
The "Inherit Rates And Activities From Object Class" is ticked in Aimee's Profile window.
She has a Buy Rate of 80 set in her Profile window.
In Server Setup: Prefer Buy Rate From Object = Yes => this means that the Buy Rate always comes from the Object in this case Aimee
When you book Aimee as Online Editor and an Activity, the Buy Rate always comes from her profile (80).
She can book herself with the Assistant Editor class, so that Sell Rate 85 is applied BUT the Buy Rate will be 80 again.
The option:
In order to allow her to have 2 different BUY Rates we need to set them up as Activities in her profile (or at least one Activity)
When Booking and you choose "Finishing" as Activity the BUY Rate will come from that Activity. However ALSO the Sell Rate will come from that Activity.
So if the Sell Rate = 0 in Eriks Activity, then it will be 0 in the Project/Booking.
Conclusion: So if a User has multiple diff. Buy rates you need to add them as Activities AND also add the corresponding Sell Rate into the Activity.