I've been freelancer for quite some time and I can't agree more with the article, I would also add few things:
Whatever you do, don't start work before you get something written for the price agreed (Purchase Order). Best, don't start work unless you get a contract specifying the scopes of the job, expected results, ways to measure completion, x% downpayment and number of revisions. Also define what happens if the job is interrupted, if the job gets out of scopes, if the client doesn't pay on time. Don't write stuff you can't get behind with (for example don't threaten with legal actions if you don't have the means to do one...)
The time when you didn't agree for the job yet is the only one when you get the upper hand. That's where you should make sure not to get screwed afterwards.
If a client talks about trust, honesty, honor, credibility, but won't sign a brief, a purchase order and terms and conditions, avoid this client. Do a contract for friends and family. Be twice more strict on terms and conditions when working with friends and family.