got an iphone? there’s an app for that! ; D seriously, when i was a freelance editor, i had an idea of an “average” amount of time a job would take. i bid on it based on that, and just worked. sometimes i worked for less than i’d anticipated because i wasn’t an expert estimator. but overall, i managed to support my kids. i sent the invoice in with the finished work. if the job was large, i invoiced in stages.