help... me...
Not necessarily going to help you, but I think not everyone knows.... and it can make people save money.
You can share your whole steam library with a limited number of friends (require to log on your/his account and "authorize" the local computer), they can play your games (and you can play theirs) as long as they are not playing anything, OR as long as you/they are offline while playing.
There is some games that interested me recently, and as long as one of my trusty friends had a copy, I could play it solo sometimes, or we could even play multiplayer using offline trick (not guarantee to work with every game, its weird af trick).