Bill saw an ad for long range WiFi antenna that will enable him to pick up signals 1000 feet away. Should he be concerned with security? Leo says no. A receiver won't extend his Wi-Fi signal. For that, he would need a Wi-Fi extender. There are several of them.
If he's looking to "borrow a cup of WiFi," it won't work, and would be rather unethical without the permission of the Wi-Fi Host. Leo recommends FreedomPop. He'll have to buy the hotspot, but after that, the data is free.