Only one is really 'wrong' even though I understood it. The correct version is: "I'll treat everyone to a beer." I'd rather say "I'll buy everyone a beer" or "Drinks are on me". Other suggestions: He was fired for always being late for work (sounds slightly more natural but your sentence is fine). What does your house cost / what did your house cost?

I'll treat everyone beer He likes walking around/in the park

*Slang in brackets () *Extra notes in square brackets [] Let's go to the bar, I'll treat everybody to a beer. (Let's go drink. Beers on me) We had to fire the nanny since she treated the children badly. [but the sentence is still okay] He was fired because he was always coming to work late [but the sentence is still okay] How much did your house cost? [your sentence is okay however]