Sql query with multi return options

I’m trying to build query that return 0 or more and return -1 if Id isn’t exists
For example:

Select Count(*)
From my table
Where id = inputId

I tried to use case like this:

Select
  CASE WHEN Count(*) >= 0 THEN Count(*) 
   ELSE -1 END
From .....
Where....

my issue is that 0 is valid result that mean Id exist with 0 columns,
I need to return -1 if id isn’t exists

>Solution :

Use a case expression to:

1. If there are values in that other column, return the count.
2. If no value in that other column, return 0 if id still exists.
3. None of the above exist, return -1.

select case when count(othercolumn) > 0 then count(id)   -- or perhaps "then count(othercolumn)"
            when count(id) > 0 then 0
            else -1
       end
From my table
Where id = inputId