there are a plethora of topics on this subject around the forum, here's the basics based on what you asked specifically:
There are 2 separate families of Phantom 2, make sure you understand the difference:
The Phantom 2 Vision (and Vision+) come with an integrated gimbal (for camera stabilization) and camera. These models were specifically designed to be out of the box streaming live to iDevices because the RC (remote control) does not run on wifi frequencies so you can use a device's wifi streaming... however you're limited in range a bit because wifi only goes so far.
The other non-Vision Phantom 2s are (I'm generalizing here) designed to with a GoPro and usually come with gimbal designed to hold a GoPro (currently the Zenmuse H3-3D or it's predecessor the H3-2D). Unfortunately the RC device for non-Vision P2's runs on the same frequencies as wifi, so you can NOT use wifi streaming from the gopro device.... therefore if you want live FPV you must add in a separate FPV transmitter on the Phantom and of course something to receive the signal on the ground (either a LCD screen or goggles). One of the advantages to going this route is you can get FPV/transmitter equipment that will go MUCH farther than wifi will.
There are a LOT of pre-made kits you can buy with cables or "fpv hubs" so you don't have to do any soldering at all although you will have to open the Phantom and plug some things in... or if you're so inclined and don't mind a couple little solders you can completely install things yourself.
this Youtube guide will give you an idea of how complicated (or not, imo) the manual process is. You'd be skipping the first part the iOSD mini install but honestly for another $80 it's really worth it to have all that telemetry info on the screen if you're doing FPV.
I haven't paid super attention to the Phantom 2 Vision+ prices but I think they're around 1200-1300 USD.
a Phantom 2 with gimbal (assuming you have a gopro already) will run you around 900-1000 USD, then another 400 or so for quality FPV kit/system. Point being, I'm afraid neither of these options is "cheap". There are cheaper quadcopters with like 720p cameras that can stream live and whatever but the Phantom isn't one of them.