Subtract value 2 from value 1 in sql

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C#

ASP.NET

SQL

Query No. 1

select sum(income) as pairs from Table2 where user_id='100001'

Query No. 2

with cte as
(
  select userid, parentid from  Table1 where userid = '100001'
  union all select t.userid, t.parentid
  from  Table1 t inner join cte on cte.userid = t.parentid
 )
   select count(*) from cte 

what i want is that join these two queries as a single query in such a way :
subtract query2 retrieved value from query1 retrieved value..

i.e query1_value - query2_value

i am trying like below. but it is giving error..

with cte as
(
  select count(*) as pair_count,userid, parentid from  user_detail where userid = '100002'
  union all select COUNT(*) as pair_count,t.userid, t.parentid
  from  user_detail t inner join cte on cte.userid = t.parentid
 )
  
   SELECT (B.AMOUNT - A.pair_count) AS DUE FROM cte AS A
   CROSS APPLY (SELECT SUM(Pairs) AS AMOUNT FROM payout WHERE user_id = '100002') AS B
   WHERE A.userid = '100002'

Error is :

Msg 8120, Level 16, State 1, Line 3
Column 'user_detail.userid' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.
Msg 205, Level 16, State 1, Line 1
All queries combined using a UNION, INTERSECT or EXCEPT operator must have an equal number of expressions in their target lists.