Buying a iphone 5s off craigslist? Help?

So im planning on buying an unlocked or tmobile iPhone 5S. Can someone give me tips so i dont get scammed. I heard people claim the phone is stolen after they sell it and the iphone becomes disabled. So i need tips on how to buy it safely

Added (1). also how do i make sure people dont claim insurance, the guy claims to have the receipt and box so is that good enough

Why wont my iphone connect to home wifi?

My iphone (new. 5s. IOS7) doesn't pick up my home wifi anymore. Like, my laptop is connected so i know it's not the wifi but when i go to wifi settings, the name of my wifi network doesn't show up. How should i fix this? I've already tried reseting my network settings. Thanks

How to get my iPhone charger to work again?

My phone always seems to die while it's charging so, I unplugged my phone and then plugged it back in, and now it won't charge at all? Is there a way to fix it?

I'm traveling to Europe and am confused about using appliances?

I'm going to both Spain and France next month for two weeks, and hair dryers and appliances are necessary, as well as my iPhone. I understand that the plugs are not the same, and adapters are needed for that purpose. I have bought multiple adapters. HOWEVER, I am aware that the voltage and currents are not the same as they are in America.

I have heard that most Apple products are "intelligent" enough to recognize different voltage, and switch automatically to avoid killing the device. Is this true?

Also, I have bought a Step Down Converter to decrease the voltage from the European amount to the American amount. This is where I'm confused. On my converter there is a label listed with:
Input: 220/240 V
Output: 110/120 V
Power: 200 Watts Max

I lucked out and my hotels all have hair dryers provided, but my hair straightener and curler are both labeled 120/240 V… I don't understand. Is this the Input for the converter? Will it be safe to use with the converter in Europe, or not? I might just go online to Conair and purchase another converter if necessary specifially for their products.

Can I sync iTunes to iPhone w/o CPU?

I have an iPhone 5s and would like to get my iTunes music onto my phone. My computer no longer works and I am looking for a way to still get my music transferred. Is there a way to do this?

My iphone won't let me stream videos on youtube. How do I fix it?

My iphone won't let me watch videos from the internet etc youtube. When I click on the video nothing happens. I thought it was just Safari so I downloaded Opera Mini web browser and tried to watch a different video. When I clicked on the video the screen goes black. I can exit it though by pressing home button but please help me! (By the way, I can surf the web just fine)