So, what's the $$$$ price of a new one that fits your needs?
How much $$$$ will the "old" trailer (which looks to be in excellent cond) sell for?
There may be taxes, delivery charges, these are numbers too.
What is that $$$ difference?
And costs without numbers include; "craigslist effort", no-shows, no-sells too. It does take time and can be significant. Unless you weren't doin' nothin anyway. Prob NOT the case.
That is the impetus for modification. Plus your tolerance and ability to carry out a quality mod. Also painting. If your 16ft trailer has 5200lb axles thats good, and I like that forged hitch. But what are the numbers?