IMO, you can call this term black and white. Everything will be documented and on paper when you've got some dealings to do.
And that's really the first thing to do when things go south and that's to seek legal counsel that will help you how to resolve these matters or how to counter that deal that went against your contract.
I've been into many business deals and fortunately, I didn't have to come up with this kind of situation.
If you know that you are dealing with good amount of money and a lot is at stake, a lawyer is indeed needed in your transactions. I can understand if you are only doing small business as you can manage it on your own. But if there are other stakeholders and they have vested interest in your business, it is better to have a lawyer that you can go to. You'll never know what will come up later on. You may need them even for consultancy services.