No chance for an individual in the SPX pit now.
First you will have to pay a trading permit fee of about $7,000.
Add another $3,000 for technology,
You will also have to join a JBO/Prop firm that currently has traders on the floor. There are still a few. The clearing firms will have no interest in you as an individual no matter how much capital you have. Id say minimum capital would be at least $250,000 if the JBO was interested, maybe much more.
Assuming you finally get to the floor you will be standing in a pit and your advantage would be being asked a market on very large trades. Would you willing to buy 1,000 back month options with a small edge with no way to get out?
There is very little retail paper announced in the pit as smaller order are filled electronically.
The big guys can take down a position and adjust their markets on other products they trade.