mj -
Just wanted to echo what hunterridge said about the 16' trailer. You might be just barely OK on the weight (even with a box blade or bush hog), but I think you're going to be too tight on the length. Keep in mind that it's nice to have some room to play with so you can get your tongue weight just right, and don't have to worry about having your bucket crunch your tow vehicle on a tight turn.
Again, I'd hold out for an 18-ft. 9,000 lb. (4 1/2 ton) trailer. I paid $2,000 for mine in excellent condition.
Judging by the uses you have in mind, you're really going to be loving that machine, and yep, tractors sure are nice these days aren't they?
Have fun, John