No, you do not need Wi-Fi in your house to use your smart phone. You will likely need a Sim card so you have access to your network. I believe some Verizon phones do not need Sim card however you will need access to a network to use your phone for anything internet or call related. Good luck!
Short answer, no, but it helps. Depending on which service you choose for your smartphone, your phone will just use the cell-service-providers Data. Wifi would allow your phone to run a lot quicker while using certain things like YouTube, apps, or any internet services. Did you have any phone in particular you were looking at?
If wanting to use the internet yes you need Wi-Fi and also for making calls , unless your service is able to connect to 2G/3G/4G/LIT then you don't need Wi-Fi but the phone will work much slower without Wi-Fi
If you plan to access the Internet using your phone
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