I haven't played rust but here, normally, you can play solo, take a break and when you come back everything will still be there. As a matter of fact, you can even create a new world and move there with your same old character and then come back to the old world with that character or a new one even and your structures will still be there.

That said, the game is Early Access so it's not impossible that after a crucial update worlds have to be wiped. I'm not saying it will happen at some point I'm just saying it's something to be expected with EA games.