The problem with your business is that you take projects that don't have formal statements of work.
Professional consultants always work under a SOW, either as an exhibit to the standalone contract they have with their clients or, for major or longstanding clients, as the "per project" contract that accompanies a master (MSA) contract.
The whole reason you write a statement of work is so that the client can't reasonably claim that an "extra" they want is actually within the original scope of the project. If you chronically say "yes" when your contract (and good sense) says "no", then the problem isn't with how you quoted the rate; it's that you're unprofessional.
I'm sorry to be harsh about it, but the histrionic tone of your comment ("working for minimum wage") seemed to justify it. If you're even coming close to working for the rate your expected full time salary would back out to, you're doing something so wrong as to warrant shouting.
Professional consultants always work under a SOW, either as an exhibit to the standalone contract they have with their clients or, for major or longstanding clients, as the "per project" contract that accompanies a master (MSA) contract.
The whole reason you write a statement of work is so that the client can't reasonably claim that an "extra" they want is actually within the original scope of the project. If you chronically say "yes" when your contract (and good sense) says "no", then the problem isn't with how you quoted the rate; it's that you're unprofessional.
I'm sorry to be harsh about it, but the histrionic tone of your comment ("working for minimum wage") seemed to justify it. If you're even coming close to working for the rate your expected full time salary would back out to, you're doing something so wrong as to warrant shouting.