How much should I charge?
Richard Harrington has a great 5 minute excerpt from his Lynda.com series Budgeting Video Projects, on how to plan and set your business rates. Taking the time to watch this and then think carefully about your own rates will be invaluable in helping you become and remain profitable.
Determining rates for services
Budgeting Video Projects | by Richard Harrington
View this entire course and more in the lynda.com Online Training Library®.
I find it a lot easier after you have done a few free lance jobs. If you can even do them for free and get good critiques from the person you provided the job for. Ask what they may have paid for the job.