I think I'm going to start putting this kind of advice here because I lead myself down the stupid path often enough that I think it's only fair I started posting warnings for all those who may be following.
Some advice on doing commissions, professional, commercial and contracted art.
Make sure you are paid what it's worth to you.

Do a test run on a portion of what is being asked of you before you say yes or no. Time yourself. Multiply that by the volume of work you have to do, so you know about how long it will take.

Once you've done that, multiply that time by the required minimum wage in your state/country. If you are being offered less than that, then you should inform the client. If the pay is not raised? Run. Head for the hills. This is a contractor that doesn't give a shit about you and is willing to sacrifice you, your time, and your dignity to get what they want.

If you are okay working for this rate, let them know that a pay rate less than minimum wage, or less than a decent professional rate, means they waive the right to request changes, adjustments, and edits. If you can't expect professional pay from them, they can pretty much get what you give them and have no right to complain as though this is a professional contract.

If you are okay with acting as though all is fair and they get to edit and change all they want, regardless of crunch on your deadline, time lost from the rest of your life, and strain on your sanity ... then don't say I didn't warn you.

Select a pay date and due date that works for both you and the client. These dates need to be firm. You can't be late, and neither can they. Everyone has to be honest. Arbitrary dates don't inspire honesty in anyone. If the client says, "I have up to three weeks to pay you after you give me the final product." Run! What that means is they don't have the money now and may not when the time comes.

It's perfectly fine to ask for some, if not all, of the payment in advance. Think about it like the business transaction it is. You wouldn't order something online or go into a store to buy something and expect to get the product first, would you? Then neither should they!

Do not give the client the final product until you have been paid completely! Just don't do it. Once they have it in their hands, some clients think they don't have to pay you. They can just run off with it, and if the fees are less than a certain amount, you can't really take them to court over it. You're stuck.
Now I'm not saying that all or even some of this has happened to me lately. This is just what I have learned (far too little and far too late) since I started doing art for pay. It's stuff I wished I'd known before learning it the hard way.
Special thanks to *
Altalamatox (by they way, it's as fun talking to her as it is to look at her art) for setting me straight on a few things. I needed that reality check.
Do as I say, *not* as I've done,
-Nuisance
When dealing with people that are dear to you- Set out a price and work things out in a way that you agree is fair. I can understand giving a break to those you love. But please, for your own sanity's sake get a written agreement if not a formal contract, and if it's something significant, insist on payment before you deliver. If you're willing to let them delay because there's an issue, don't deliver until they can pay you. Perhaps it's just bad luck, but I've repeatedly found that if someone thinks that you consider them dear in some way, not all but a good few will drag their feet because you let them. I'm still waiting on $75 (for a shiny worth twice that in time alone) from last June because I thought I'd give a friend a break.
I admit that I do my best to be optimistic and to think the best of folks, but getting stepped on like that sucks and can ruin a good friendship. Good boundaries and knowing your limits, like not delivering until you get paid, can help minimize the suck factor.
!yoJ
great job in putting this up, will help others..
I'm pretty strict about "if you don't tell me, then I can't be held responsible for it". It's not popular with people, but it helps.
You're welcome!
(I'll say that the worst mistake I make, and I make it all the time, is offering myself too cheaply. I can only get mad at myself later on, because it's no fault of the client's, and I certainly can't suddenly ask for more during the work, because that's not fair to them/their plans/their finances. It's a terrible noose!)
I was blown away by that contract you'd written up- I've never done anything like it, and for the big projects I should. Glad you were able to iron some things out while talking with me, our conversation's been reminding me of good business practices as well!
You're always so pro about looking mistakes in the eyes and then giving them a mighty headbutt.
Still hoping your current dealings get straightened out to your satisfaction. <3
He's still waffling about dates and start times. As of today, we still have a while before we'll be asked to get started.
Keep in touch!
All in all, great advice!