During the scene after their wedding when they were in the west wing, Seadown was telling Ginny that its her money that will renovate the wing, she realizes he married her for her money. He tells her its an even exchange.
I cant seem to understand why. He has no money - is it some type of status? If so..what does he bring to the table?
Yes, it is a type of status. Her father's money has, in effect, purchased her a title in the English nobility (through her marriage).
Seadown's father, Lord Brightlingsea, is a marquess. "Seadown" is his lesser title (Earl, perhaps?), so his eldest son is entitled to use it. That makes Virginia "Lady Seadown." And when her father-in-law dies, she becomes Lady Brightlingsea or to put it more formally: Virginia, Marchioness Brightlingsea.