Reminder: contract is NOT an employee and as such is not under minimum labor rate laws. I have file my own taxes...1099 form, etc.
There are differences between self-employed vs working for a contract agency. When I worked through an agency, all of that bidding is done by the contract agency. All I did was interview to show them my face, if I had a portfolio, or examples of my work and let them know I could communicate ideas effectively.
Hypothetical example: if I work through an agency, the dynamic is different. They send me out on interviews, handle the bidding and negotiation for the rate of pay and the length of time of the project as set by the company.
I tell my contract agency when I'm available, what I expect for a rate of pay, Full or part time..and how many months I could be available. Agency arranges with company details such as negotiate pay rate, project completion deadline and level of expertise issues and specific location for work (whether an office or workbench and tools (usually not) or whether working from home is allowed or expected.
I work through agency so agency pays me. They will pay the agency, let's say $25 hr -charging the company. The company typically takes 33% give or take. and pays me $17 hr. During the length of the contact, I keep my hours (submitting to agency) and if the deadline is closing in, If not working through agency, I work whatever hours I need to do to get the job done in time.
Being responsible and knowledgeable about the process, I finish a bit ahead, present the completed project to the boss/project lead/principle manager, and wait for their response. Typically they want last minute changes or tweaks which I will do to maintain my reputation and good name. If working through agency, I let them handle negotiations for those last minute labor hours.
This is an idealized example.