Maybe you already have internet at the new house.  If you are using a wireless router at the farm, there are a few routers that spec a "free air" range of about a quarter mile.  Check your laptop to see if the network from the farm carries that far.

Can you see the farm from your house? 

I have a friend that used one of these USB adapters   at the focal point of a small pizza satellite dish for occasional access from a metal shed to the wireless router in his house a little less than a  half mile away.  He connects the USB adapter to an old laptop at the shed.  The router at his house is located so there is only one wall between the house and the dish.  He mounted the dish outside the shed pointed at his router a half mile away.  It took him a little while to get the dish pointed at his router but he reports a pretty good  connection.

Need more ideas look here:  http://seattlewireless.net/ 

If you don't have a wireless router, you might look into a linksys wrt-54gl.  You aren't likely to find these in your local best buy, or office supply store, but  a couple of these, third party firmware and line of sight between the new house and farm and you should be able to do what you want.