1800 acres - the "out of your league" comment sounds like a valid response.
Here's an ebay offering along the lines of the minimum you need.
http://cgi.ebay.com/ws/eBayISAPI.dl...loc=closed_view_item&refwidgettype=osi_widget
When I bought my first equipment in the mid 60s, met a guy who in the late 40's who was part of clearing the soon to be lakebed behind Hungry Horse Dam.
Don't know what the bid was, but his friend got the job, many square miles, with a penalty for going past the time limit and incentive for finishing early.
D9s were the biggest tractor then. They bought 4 from CAT, got a bunch of WWII surplus anchor chain (the 5 inch dia link stuff) and a few 20,000 pound steel balls and some BIG swivels. Took the a track apiece off the D9s and made a couple of D9 tandems out of them. Bought a few D8s also.
They put the ball at the middle of 2 long anchor chains and a tandem dual D9 at each end and ran thru the forest. Did not bother to log anything, pushed everything downhill into piles with the D8s and burned it all. Made big money by finishing way ahead of time and then had all those machines free and clear besides. Close to 35 miles long and about 25,000 + acres cleared.
For even that relatively small 3 section 1800 acres, yu gotta try to think along differernt lines than a skidsteer and brushcutters. The ball and chain would not leave much of a footprint. I'm thinking one (or many) of the big Cat or Link-belt track hoes with a thumb and shear attachment would give the least land impact and quickest clearing. You outa be able to buy a used 15 ton trackhoe for $30K or so and have at it.
Milwaukee land company clearcut 6 sq miles next to my cabin in the 90s'. After the logging, mostly with towers, they slash burned everything in place over the course of 4 days - D6s all around the perimiter and a fire truck every 1.4 mile. No idea what the slash burn cost or how many guys at work 24 hrs a day.
My neighbor is a retired logger and former head of the county parks department equipment operation. IIRC, his rule of thumb was you need at least a D8 and 500 operating hours per section depending on terrain.