|When setting up a LAN (Local Area Netwrok) your ISP is irrelevant, you dont even need one..|
However, setting up a LAN over a distance of approaching half a mile is difficult bordering on the impossible. The maximum distance a Cat5 cable between devices is 100 meters (328 feet). The maximum distance you can expect for wireless is about the same in ideal conditions.
However, these restrictions can be overcome with extra equipment but is it worth the expense?
If you use cable you are going to need repeaters every 100 meters. If you use wireless you are going to need hi-gain directional antennas with line-of-sight.
The only other alternative is a VPN (Virtual Private Network) but that does require an Internet connection.