jdc1 wrote:
Even better, find a used 2500 diesel
Even full timing, unless you are planning crazy numbers of miles, you likely won't recover the cost of diesel. Now if you find a deal...that's a different question.
A 3/4 ton does make sense for a full timer as it's less likely to have a "tail wagging the dog" situation as everything is bigger, heavier and stronger.
As others have said, go with the max loaded weight of the trailer for your early estimates (GVWR) and then figure out what is likely to be in the pickup (firewood, gas jugs, bed cap, etc...) as the hitch weight comes off your payload.
If you go 1/2 ton, make sure it has the heavier payload options (they can be as low as 1300lb to over 2400lb, so simply saying 1/2 ton can have a lot of variability). Payload will likely be your limitation with a 1/2 ton.