How is USCF initial rating assessed?

I'd like to start playing tournaments around town, but I'm a little confused about where I start... My chess.com blitz rating is around 1600. Do I start out at 100 and work my way up? Or can I provide my chess.com rating to give them a better estimate?

Its probably like fide. It is the average of all your opponents ratings in the tournament. Don't forget it fluctuates greatly.

Understood, but where do I start if I've never been officially ranked before? At the bottom? I'd feel guilty taking prize money for winning tournaments in the bottom brackets against people who have very little experience in chess, many of whom are very young children.

If you haven't played USCF rated games, you will be treated like any other unrated player. There's no need to provide a chess.com rating or any other kind of estimated rating.

Your rating will be "provisional" until you've played 25 rated games. Provisional ratings are calculated based on your opponents' ratings and your results. If you break even in your first tournament, your first provisional rating will be the average of your opponents' ratings. If you win every game, it will be that average plus 400 points. If you lose every game, it will be that average minus 400. 

Don't worry about taking prize money. If you actually win a prize in your first tournament, you will have earned it. And watch out for those kids, they can be dangerous!

great! thanks for the feedback and advice!

I guarantee you play provisional players now or have in the past hundreds of times and beat them on chess.com. Only difference being you may get prizes and see the players cry In person instead of via chat.