When does getting a 'prenup' or a binding financial agreement make sense?

A financial agreement can be made before, during or after a marriage or de facto relationship. (Supplied: Adobe Stock)

While pre-nuptial agreements, often referred to as "prenups", feel par for the course in celebrity circles, they can be relevant for ordinary people too.

There has been a "big uptick" in interest at the large national family law firm where Yianni Kordos is a principal lawyer.

He says for couples (or former couples), it's important to consider the "cost versus value," in their circumstances, of obtaining an Australian version of a "prenup".

Called binding financial agreements (BFAs) in Australia, they take time and money to acquire.

Here's how they work and when they might be relevant to use.

While BFAs are colloquially referred to as 'prenups', Associate Professor in law at University of Technology Sydney, Miranda Kaye says that term is a bit inaccurate because they are more broadly used than just before a marriage.

"They're essentially a contract that can be done before, during or after a relationship."

And marriage is not a requirement, Ms Kaye says. De facto couples or "to be" de facto couples have also been able to enter into a BFA since 2009.

A BFA is "a contract between you that deals with your assets … and how they're going to be distributed in the event that you aren't together anymore," Perth-based family lawyer Ella Hickman explains.

If done correctly they remove the Family Court's jurisdiction to come in and say how to divide assets, Ms Hickman says.

Research into the use of financial agreements made before or soon after marriage or entering a de facto relationship, conducted by Ms Kaye and other academics, involved interviewing 40 family lawyers in Sydney.

Yianni Kordos says there are two parts to the cost of a BFA, drafting the agreement and then the provision of independent legal advice. (Supplied: Yianni Kordos)

While they didn't all disclose the cost, most of the solicitors interviewed said they charged a minimum of $10,000 to create a BFA, Ms Kaye says.

Mr Kordos says a "straightforward" contract without back and forth negotiating can cost between $4,000 and $5,000.

But when lawyers create a BFA they are only representing the member of the relationship who instigates the BFA, and Ms Hickman says a lot of people fail to factor in the cost of independent legal advice for the second signatory.

"The other party actually has to go to a different lawyer and have them review it, have them potentially make changes, enter into some negotiations, give you your advice, and then sign the certificate of advice … [for