A person who often has sex out of charity or pity in spite of having insufficient sexual attraction. The not-for-profitute often feels like they ought to have been payed, but refuse to receive payment as their sexual performance is a gift of charity.
"Kev, dude. Your face is glowing; what's good man?"
"Man, I dicked Brittney last night. She's like a 10. I'm like sexy and I never even knew."
"I hate to break this to you Kev, but Brittney's a not-for-profitute."
"Oh. Dude, I'm not even mad though. Her tits were bouncin'."
The oldest two professions are prostitutes and politicians respectively. You pay them both, you choose them both, and they both look to fuck you. Therefore... they are politutes.