1. Mary thought their business venture was promising, but she didn’t have a lot of money, so she told them to deal her out.
2. If you’ll excuse me for a moment; I’m going to make a phone call. But I want to play this round of cards, so you can deal me in.

The expression originates from the idea of being included or excluded from a hand of cards in a card game like poker, and is still in reference to card games. It is also used figuratively in business ventures and other group activities.