My dad and I have just bought a gaming pc to share between us and we don't want to share the same steam account, but we also don't want to have to buy a game on my dad's account and not have it work for my account. shouldn't it just save to the desktop so we can both play the game but just on different accounts? We want to do this because single player games won't allow us to start two independent games for myself and my dad on the same steam account.
Normally, a Steam game will only work while Steam is logged into an account, and that account has a license for that game (from being gifted it, buying it or redeeming a CD-key). However, you can configure Steam Family Sharing to share games between a limited set of accounts on a limited set of PCs; however, if the person who shared his library with you is currently playing a Steam game, even a F2P one, you will not be able to play the games they have shared with you until they stop playing.
If you're using the same PC and won't be playing games simultaneously, you can use Steam Family Sharing. Both you and your dad can buy your own games on your own accounts, but you both set up each others' accounts with Family Sharing and then register your shared gaming PC. Both accounts will then have access to the same set of games without needing to change users.