Are these sentences OK?
we are short a staff.
I'm surprised you asked for my help.
He used to sit here all day waiting for you to return. (a dog)
I don't know everyone who goes in and out of the building.
Why would someone want to steal something who's got everything?

Question

Are these sentences OK?
we are short a staff. 
    I'm surprised you asked for my help.
    He used to sit here all day waiting for you to return. (a dog)
    I don't know everyone who goes in and out of the building.
    Why would someone want to steal something who's got everything?

Answer

Agree with below. I think #5 sounds natural this way...

1. We are short-staffed
2. Correct
3. Correct
4. Correct
5. Why would someone steal something that already has everything?

Answer

We are short -staffed.

All others are OK but the last one is a little awkward. Laura’s rewrite is better.

Answer

1. We are short a staff person. OR We are short-staffed.
2. correct
3. correct
4. correct
5. Why would someone who's got everything want to steal something?