Do some searching on here for Ubiquiti.  It's discussed regularly. 

If you're looking for a single router to service your entire 4 acres you're going to be dissapointed.  You'll be even more frustrated trying to get a single router in your house to give you service inside metal buildings.  If you are able to defy the laws of wireless signals and get a signal in those buildings (without a wireless bridge) you'll come to find out that you don't have enough signal strength and/or bandwidth to handle a camera stream.

There is no "one size fits all" answer to outfitting a farm with full coverage network access.  Every single setup I've done is different.