How to offer free wifi over a mile?

[Macdonjo]

I'm considering offering free wifi to my customers on our property which will require about 3/4 to 1 mile signal range. I'm wondering, what would a system like this cost hardware wise and who sells this type of equipment. I don't think it would be a router that I'm after, right? Or do routers get this strong?

 

[USAFRet]

What does your ISP recommend? This is not a new procedure for them.