Lots of good advice here, perhaps mixed with a small bit of paranoia. Don't worry--I'll explain.
But first, my trailer history. In 2013, I wanted to buy a trailer to tow my own TJ. I did consider used ones, but the small drop in price compared to new was typically offset by the amount of money I'd need to immediately sink into them to bring them up to snuff. I quickly decided buying new was a better overall value, so that's what I did.
I was considering three brands: a Big Tex from Lone Peak; a PJ from Wasatch; and a Big Bubba from, well, Big Bubba. They were all priced close enough as to not matter, so it came down to the trailers themselves. The Big Tex and Big Bubba were virtually identical--indeed, had you peeled off the labels I probably couldn't tell one from the other. The more I looked at the PJ, the more it stood out. It was better than the other two due to a host of little details: flush-mounted lights all around, removable aluminum fenders, a pivoting jack rather than a fixed one, and so on. It set me back $2500, but I feel I got a very nice trailer and felt it was worth the trip to Layton to get it.
My PJ is a 16' 7k dual axle (with brakes only on one):
This trailer is perfectly adequate for hauling a built TJ, and it has also hauled a number of other vehicles over the years. It weighs about 1800 pounds empty, which leaves me with 5200 pounds of cargo capacity. My TJ weighs 4020 pounds in daily driver configuration; loaded up for trails will push that up to around 4100 pounds. This is obviously well withing the design limit of the trailer, and why I said this trailer works so well for a TJ. My ramps slide out to the side, and that has also worked well for me over the years. As the photo shows, I am a strap guy rather than a chain guy. I use four independent straps for safety and redundancy, at shallow angles, and I always carry at least one new spare strap in the tow rig just in case (though to date I've never had any sort of roadside strap emergency, probably because I inspect those before use and replace anything that looks even mildly iffy).
And now for the paranoia: tires. My trailer came with what the internet calls the single worst trailer tires on the planet: Power King Towmax tires, C1 load rating (my size is 205/75-15). Yes, they are Chinese. Their rated weight capacity is 1820 lbs per tire, which means all four just barely handle the 7k rating of the trailer. But despite all that, these tires gave me over five years of
flawless performance before finally needing to be replaced earlier this month. I attribute that to three things: I always checked their pressure and made sure all were at 50 psi before each use; I didn't overload the trailer (except for only a couple times); I keep my speed to 70 MPH max while towing.
I just replaced them with a new set. Some folks here (and elsewhere) suggest using regular truck tires on your trailer. But every time I did research with an actual tire manufacturer, they always say you should use trailer tires on a trailer due to the different stresses that tires on a trailer encounter compared to tires on your truck. In the end, I bought more trailer tires... but I upgraded to a stronger D1 load rating (still in my same size). This increases each tire's load capacity from 1820 lbs to 2150 lbs. It seemed like a wise idea, definitely worth the few extra dollars per tire. I ended up with Carlisle Radial Trail HD tires, which are supposed to be some of the better (best?) trailer tires out there. Time will tell, I suppose.
Anyway, that's a quick summary of my own adventures in trailering a built TJ. I hope it helps.