You need to know what your payload capacity is on the tow vehicle. If it's not on the sticker on the door pillar, go to a scale and subtract it's actual weight from the GVWR. Once you know the payload capacity, you can shop for a TT and not get into trouble as all too many do. Forget about the towing capacity. The payload capacity will be the limiting factor on a TT.
Never go by dry weights of TTs when shopping. Use the GVWR. For an estimated actual tongue weight, take 12-13 percent of the GVWR and see if you have the payload capacity for it. When looking at payload capacity of the tow vehicle, you must include weight of driver, passengers, pets, groceries and camping "stuff" in it as well as the weight of the hitch shank and spring bars. Look at cargo carrying capacity of TTs as some have lots of CCC and some have little. When it's on the low side, it's easier to load up to it's GVWR. In some cases, full holding tank(s) can even put you over the GVWR (not good).
There is an excellent sticky on how to set up a WDH in the towing forum. Just don't let a dealer do the setup. You should learn how to do it. You'll want some sway control and add-on friction bars are popular for TTs on the smaller side.