He says it's the chance of a lifetime.
5 seconds sound clip from the It's a Wonderful Life (1946) movie soundboard.
You can hear this line at 00:49:37 in the Blu-ray version of the movie.
Quote context
[...]
- Well, this is the biggest thing since radio, and I'm letting you in on the ground floor.
- He says it's the chance of a lifetime.
- Now you listen to me. I don't want any plastics, and I don't want any ground floors.
- I don't want to get married, ever, to anyone. You understand that? I want to do what I want to do.
- And you're... And you're... Oh, Mary, Mary...
[...]