$6000 is a great down payment on a tractor that will last him for generations. Currently Mahindra (and others) are offering 0% for 36 months or 2.99% for 60 months. The amount of interest paid over the entire term on a 60 month loan is less than it would cost you to rent a tractor for a week.
If you don't like the idea of payments, probably a full size 60's or 70's farm tractor with a loader would give you the most bang for the buck. Gray market and Chinese are less money, but not always a better value. It depends on the model and especially dealer support, and if you are willing to be patient for parts and service.
One thing about tractors is that they hold their value. If he buys a usable used machine now and gets a decent deal, he can probably sell it in a year or two for about what he paid, and use that money to upgrade to what he really wants.
Good luck,
