Do your homework (Hint:the internet is your friend), and buy used. That $18,000 will go almost, if not twice as far as any "Deal" you find on a new one. New TT warranties are close to worthless unless you buy from the dealer down the street an he happens to be one (of the very few), good guys. In many states there is no sales tax on private party sales which saved us an additional 9%.
A lightly used 2 or 3 year old TT should go for 60 cents on the dollar from the discounted new price (think 30 to 35% off of MSRP). Most will come with a WDH and lots of gear - sewer and water hoses, chocks, jacks etc.. Buying new may or may not get you exactly what you want but with a little research and the willingness to travel for a deal you will pay about half.
Good luck! :C