The two problems we see with trailers are sloppy construction which is usually just annoying. Like having to secure electrical wires.
The other problem is from abuse... some can take it better than others. A trailer that is marginal won't take overloading... things start to bend.
That said... I don't know how some of the finished trailers can be sold for less than the price of me buying the components.
How hard do you intend to work it?
My neighbor tows his 24' tag Interstate for a living... maybe 25,000 miles a year. Over the last 6 years, he has had to change a number of tires (buys better ones now) replace wheel bearings and replaced both axles and springs with brake hardware once.
His trailer is at or over the limit weight wise.
