As far as normal metro north parking, there is free weekend parking only. White Plains has no street parking, meters galore. I believe (though I have never done it) that there is a lot off the Bx River Parkway at the Westchester County Center that offers daily parking fees, I would contact them to verify. You can go on a friday and pay for parking for one day at the station, and because it's free over the weekend, you wouldn't have to worry about it saturday/sunday only.