Any private sale of used merchandise is 'as is' unless the seller writes down a specific warranty. That warranty is only as good as person selling the item, so may be worthless anyway. I don't know how much this TV retails for, but if you purchased an item for $1,000 with a one year warranty and it lasted 5 years and goes out that's $200 a year. If you buy a used one for $200 and it lasts longer than a year, you are ahead. And, if it's 'hot' ~~ a receipt isn't going to help you retain ownership if they ever found you.
That said, buying used items is a great way to get things you can't afford at regular price. I've probably bought more used items than new in my lifetime. You know, once it's in your house for a few months, it's used anyway. If you do your homework, MOST of the time, it will be worth the $$$.