KZ went through a lot of financial trouble in the last recession in the US (2007 and on?). They cut corners a lot to save money and stay afloat. I know someone with an '09 KZ TT who had plenty of issues. An '07 might predate that tho.
The frame is something I would look at VERY closely, especially around the spring hangers where they can develop fatigue cracks. They have the type of I-beam that is made from 3 pieces of 1/8" sheet steel welded together and look like a regular rolled I-beam. These frames flex a lot more. Also look for spring hangers bent to one side. I would HIGHLY recommend that you have a certified frame & axle shop inspect the frame because there can be issues that you won't be able to find. Frame flex can also cause failure in welds in the aluminum framing of the superstructure.
If the spring bushings have never been replaced, I guarantee they will be completely worn out and may have damaged the leaf springs & shackles. Our bushings were totally shot in just the 2K mile trip from Indiana to the dealer.
On any older TT, water intrusion is a major concern unless it has been regularly inspected and caulked as needed. Even if you have some experience with RVs, I would also highly recommend hiring an reputable RV tech to do an inspection. There's just so many things that can be a problem and you may not find all the important ones. Spending $200-300 now could save you thousands of $$ later.