I'm building a 3500lb trailer. I looked at some of the local ones, they're all junk. Light duty units with shot bearings, worn out tires, rusting slowly to death. Wish somebody near me sold trailers for $350US, the local Home Depot sells light duty trailers for $1100CDN and they look like they're made of paper. I honestly don't know why trailers are so dear here. Must be demand.
The good ones either get snapped up in an eyeblink, or guys are asking near-new prices for them, but they still need work to be safe. I talked to a trailer dealer, he says they never get used utility trailers in anymore. Showed me one brand new H&H unit for $1600CDN that was 2000lb rated, already had 3" rust patches all over it, despite having big "Dupont" stickers all over it like the paintjob was a big deal. Sides looked kinda flimsy. Screw that.
So I bought a bunch of metal, got some plans off the web and started building one. I have most of the parts/supplies already, the cost is projected to be about $1400 total. I saw a used 3500 selling for $1800CDN the other day.
Even if I only broke even, I've learned a lot about metal fab and welding, and had fun building something useful to boot. I'd try like hell to buy a good used one, but if it doesn't work out and you have to make one, don't sweat it.