Think its weighs around 5k, how much weight can it take? Can they go 2 to 3 K on the gooseneck, weight distribution to the truck?
What kind of trailer and pickup or truck?
There's a lot of variables in a complete answer. I don't think there's a standard on the manufacturer's ratings, some are rated for the full amount the trailer can carry, other's may count on deducting the amount the hitch is carrying. If you add the total capacity of the axles together plus the amount permitted to be on the hitch you'll have your total allowable gross, then deduct the weight of the trailer and you have your payload capacity. Make sure the tires are rated to carry the total weight of the axle rating. Once you've determined the payload capacity you'll have to position it properly to distribute the load correctly between the axles and hitch. All of this is to keep DOT happy if you're stopped.