It's helpful (especially in cash?) (3)
I believe the answer is:
tip
'especially in cash?' is the definition.
The answer and definition can be both related to property as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'it's helpful' is the wordplay.
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'helpful' becomes 'ip' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
't'+'ip'='TIP'
Can you help me to learn more?
(Other definitions for tip that I've seen before include "Clue" , "End; overbalance" , "Empty" , "Hint, suggestion" , "Useful hint; end" .)