A goose neck is also known as a fifth wheel. Its the sort of trailer with a hitch that connects over the bed of the truck rather than to the bumper.
Check out Adam trailers. We just bought a two horse, stock type, gooseneck trailer with a small tack/living area up front and a small tack area off the back for about $11,000. They are very well made trailers and we got quite a bit for that price, especially since it was brand new. We also had an awning added to the side.
I don't know if you are looking to haul horses, but these come in different sizes and you can take out the horse dividers to allow for more room to haul whatever you want. We were thrilled when they came out with the two horse slant. You can't find those all too often in a gooseneck!
Good luck, and let me know if you have any questions!