Email : "Hey, I have an idea for a card game."
Me : "OK, What is it?"
Email : "Could you add a donate button, as I'm strapped for cash."

No.

Simple as.

If you want million of dollars from a card game, go and ask someone who makes millions of dollars from card games.

Don't come to someone who makes nothing but freeware, and suddenly expect them to write an entire game for you, then magically send you the proceeds.

If you want the proceeds, I'll happily send you the bill for my server costs.