In this context, no matter the games of language
I do not see any meaningful difference at law
between a "referral fee" and a sales commission.
In this context, even if all you do is introduce buyer and seller (or their respective agents),
and the result of that is a payment to you (by either party), then you are involved in the transaction.
I suggest that this is especially the case if you do it repeatedly and in an organised way.
And I suggest that that brings you within the scope of Part III of the Real Estate and Business Agents Act 1978 (WA),
and the requirements it contains for licensing.