How, and why?
It seems like whenever a celebrity dies, there is a small group of people who claim that the death was faked. The typical reason given is that "so they can live out their lives in peace." This is patently ridiculous. If a celebrity wants to live out their life in peace, they can just retire.
A more common reason why people fake their own death is for the insurance money. Someone with a lot of debts may not feel like they have very many options left. Many people commit suicide under those circumstances. But if you can make it look like an accidental death, your family gets the insurance payout (which they can hopefully use to pay off your debts.) This way you lose everything… except your life.
It seems that the most common and foolproof way to fake your own death is by an at-sea mishap. Charter a small private boat, bring your own inflatable raft, take the boat out to sea, hop onto your raft, cut the boat adrift, and motor back to land. Eventually the boat will be found without you on it, and the authorities will assume you fell overboard. Or be prepared to take advantage of a disaster.
It takes years for someone to be officially pronounced dead when this happens (meaning years before that insurance payout takes place). But it has the advantage of providing a plausible story for why there is no body.
The problem with claiming that Paul Walker faked his death is that today's forensic science is insanely amazing. We are way beyond identifying bodies by their dental records. Just the tiniest bit of bone marrow or tissue left on a body will provide ample DNA for a forensic analysis. You can't just swap your clothes with a dead hobo and call it done, like in the 1920s.
A bigger problem is life after your death. You will have no verifiable identity, no work history, no credit history, no way to get a car loan or a credit card or a home loan. You will have a hard time getting a job or finding a place to live. You will be stuck with working under the table or service industry jobs, and probably living in a shared rental through Craigslist.
And most importantly, you can never contact your old friends and family again. A single postcard, a single post on the internet, just one little text can ruin the whole thing. What a lonely life it would be.