The profile rate is the hourly rate posted on a freelancer's profile page.
A freelancer may change thst rate at any time.
When a freelancer applies to a job posting, the freelancer may leave her profile rate alone as the bid rate. Or she may change it.
This is allowed.
Denise has her profile rate set at $10/hour.
Denise applied to a job posting to write blog articles about cats.
Denise likes to write about cats, but this posting requested a person who can write about Siamese cats.
So Denise decided to change her rate and ask for $20/hour.
The client is allowed to hire Denise at $20/hour.
Or more.
Or ask Denise to work for less than $20/hour.
Or ignore Denise's proposal entirely.
