Besides the obvious "a good one" ( my first was a 2 inch hitch that bolted to the frame, the second was factory built to the frame)
Check the law in -each- state. Some states only allow boats or water-craft for the 2nd trailer, many states simply don't allow it.
2008 F350SD V10 with an 2012 Arctic Fox 29-5E
When someone tells you to buy the same rig they own, listen, they might be right. When they tell you to buy a different rig then they own, really pay attention, they probably know something you don't.