You and I are going to quarrel - that's rich (4-2-2)
I believe the answer is:
well-to-do
'rich' is the definition.
(I've seen this before)
'you and i are going to quarrel' is the wordplay.
'you and i are going to' becomes 'well' (we'll - 'you and I are going to' means 'we will').
'quarrel' becomes 'to-do' (I've seen this before).
'well'+'todo'='WELL-TO-DO'
'that's' acts as a link.
(Other definitions for well-to-do that I've seen before include "Moderately wealthy" , "Affluent" , "Financially comfortable" , "with a lot of funds" , "Fairly rich, prosperous" .)