If you are going to buy new or used, do your homework and know what you are getting and what you should pay for it. There are many options on new trailers and those options add up or simply are not worth what the dealer charges for them.
I don't buy into the saying that if you are a first time buyer, you should by used. I'll occasionally look on Craig's List and see older models of the same TT I have listed at prices higher that I paid for mine new. We chose to buy new because while I am mechanically inclined, TT's were new to me and I wanted the peace of mind of the factory warranty (although our Jayco has never had an issue in over 2 years).
As others have stated, if you find a used model you like, have an independent mechanic or friend that is RV knowledgeable look over the unit. Finding a reputable dealer that will stand behind their sale is a must.