Rocker Panel Rot

Both sides are pretty rotted out; passenger side has a 4" dia hole. Is this a common site for rust? I'm guessing cut & weld a stock panel back in? Any options would be appreciated...

That is the fix, and yes, a common event.

Make sure you get all the rust out or it will be right back at you.

Very common. You can buy an aftermarket rocker panel for fairly reasonable money, but the complete piece is very extensive, and requires a great deal of cutting and weld breaking to replace whole. You'll probably be better off cutting it down and welding it in differently. You'll see what I mean when you see the part. If you only have localized holes, you're probably better off cutting out the rot and patching with individual pieces.

Try to catch it early, because when it gets really bad it eats off the unibody flanges at the bottom edge, and you'll be left with nothing to attach to.