@caterpillar145 You don't have to buy Sims 4 or any content a second time. Your account owns the game, not your computer, and you have the right to install it on as many devices as you want. (I've installed it in half a dozen different environments for various reasons.) You can only play on one computer at a time, because you can only be signed into your Origin account on one device at a time. But you can have the game installed on as many computers as you like.
You can also transfer your saves to your new computer: they're in Documents\Electronic Arts\The Sims 4\saves.