Right - work on the wording, but absolutely keep the sentiment. You are clearly valuable to the people using your skills for their own profit. You deserve compensation and respect for the time and effort you put in. Regardless of how well intentioned they seem, be incredibly insistent on payment for your work. Ideally, negotiate pay before any work is done. If they resist this, you need to walk away.

The concept of "fuck you" is important here, even if the specific words are not.

I did subcontracting work, several thousand dollars worth, for a friend of a friend. I sent the bill as our contract stated and.. crickets. Bill wasn't a surprise, I send weekly estimates.

I wait 30 days before I start in with the threats of penalties and late fees. Eventually I get back a sob story that the directs father had passed unexpectedly.

Now, I'm sorry his father passed. However, he collected the money in full from the client.. so it wasn't like that was the issue. I came back with a sincere note telling him I'd be happy to give him 60 day extension, no fees or anything, so he could mourn and all.

He sent me to his lawyer.

Of course signed contract, with weekly estimates, bill of work, etc. His lawyer offered, in 60 seconds of picking up the phone to "settle" for the original billed amount with no fee.

"Fuck you, pay me" is good advice to repeat to yourself in your head.