How to Wi-Fi hot spots work/what one should I get?

Would it charge to my house bill? I have unlimited Wi-Fi at my home so would that matter? All I need it for is my iphone because my plan can't be updated until May, so until then I need a Wi-Fi source at all times while I''m without a data charge. My friend said he bought a Wi-Fi hotspot and never really uses his Wi-Fi unless he forget the hotspot at home.

Other than that what reliable hot spot should I get?

There are some free hotspot software. You can just install it and activate it, it will make the computer to be a router, thus devi ces can share network connection