You must have a repeater. This repeater you must placed in the middle of radius of the transmitter. Repeater is hard to buy, coz of the cost and usually only buy by the ISPs.
Alertenatively you could buy several WIFI router which have the capabalities to repeat the wave. Usually the standard radius of coverage is 100 meters on a openfield. If the radius of coverage you want to cover is 1000 meter than you have to put this low tech router every 50meter. But if you get 1 high tech repeater, maybe you can cover all with only 1 unit of repeater.
If you are planning to have some sort of token for you users, then you have to get 1 pc acting as a server to control your customer's usage and access. If you are planning to us windows as the server OS then you have to be prepared of the software cost ranging from USD100 to USD400. but if you are planning to have linux then there's a lot of free software's around for you to choose..