Haylie Duff -- I'm Selling My L.A. Pad ... Just Like My Sister

Haylie Duff -- best known as Hilary Duff's older sis -- is trying to unload her Toluca Lake crib for $1.8 million ... just months after her sister sold a home in the same area. Haylie bought the 4,064 square-foot-pad 4 years ago -- right around the…