I believe the $1000 price is too low. If in good shape, $2000-2500 would be in line with a good price. I assume with a 4' beaver tail, this is a deck over wheels type trailer? Are ramps included? Are the tires E rated or G rated? For a 14,000 lb trailer it really needs G rated tires (3500 lbs per tire rating) for the trailer but many only have E rated tires. G rated tires cost considerably more. Is it a 12" or 8" gooseneck frame? Is it a fixed or flip-up beaver tail? Spare tire? Chain tray? Tie downs? All these options keep adding to the price.
I bought my used, one year old 32' dual tandem axle, 25,000 lb GVWR, gooseneck with fold down beaver tail and ramps for $5000.