Found exactly where the leak was. The previous owner tried to seal it with silicone, but the area is below the screen frame and he didn't remove the screen and fill the hole. He just squeezed silicone between the bottom of the screen and sill blindly and called it a day. The screens were adhered to the sill, but the leak was not covered.
He didn't disclose the leak either. I'd kick that old bastard in the nuts, but death already came for him, so not much I can do.
Who's v up to help me dig up a grave and kick a corse in the goo sack? There $40 in it for you.