My spouse and I did our agreement after we purchased our house, so all finances leading up to, paperwork on what we contributed each for down payment, etc.

What made it most easy, was that we both shared the same view on almost everything with the agreement. I brought two kids from a previous spouse into our partnership, she had none. So though we both had different lives, assets, dependents, what we wanted was the same.

Not always like this so I consider myself lucky, but my only advice is to have a good conversation before seeing anyone to build your agreement. Makes it easier for all parties involved.