I advertised mine in Horsemart & the first person who came to view it bought it at ther full asking price.
Put as much information about it as possible in the advert, think of everything you would want to know & ensure you include it. In particular give internal measurement of horse area, particularly height. Take some nice pictures, Horsemart allow 3 photos so take one showing front & side, another showing horse area & a third possible showing living.
Horsemart sold it within a week. I also made a photobucket account witha video of me doing the ramp and loads of photos and put that in as the website link that you are allowed.