Client: I know the site is done but can you do another two pages for me?

Me: Sure based on the details you gave me it will cost you another $250 for them.

Client: Ok, that sounds good. I'll send pay you for the site after you do these two other pages.

Me: Sorry, you would need to pay for the completion of the site first.

Client: That's SO RUDE, you are immature and completely unprofessional and should get therapy!