Nice to Join the group

[bEnA]

I want a toy hauler to carry my Honda Goldwing which weights 900 lbs

The 2017 Ford F250 Gas 6.2 sez it will 5th wheel tow 15,000 lbs..

how much weight could my trailer max out at... it will be used maybe 4 times a year

I live in Dallas TX

[wingnut60]

At 15000lbs, the pin weight COULD be around 3000lbs, if loaded heavy. If you would be traveling light except for the GW, then might be able to do it.
Find out the rear axle weight rating (RAWR) on the 250, then you will need to know close as possible how much the weight on the rear axle is without the trailer on it. Rating less the actual weight gives you the amount left to use for pin weight.
Lots of 250s are towing 15k fivers, some are over on rear axle weight by a little and some by a lot.
One thing you should NEVER do is have more weight on the rear axle than the tires are rated to carry--and that number is around 7500lbs.