Then I believe there won't be complications, it's like signing an agreement, already at the beginning you know what is obtainable from it and won't expect too much, it just reduces disappointment, because you don't Sign an agreement hoping that the terms and conditions will change somehow, it's only when the parties involved decide to update the terms.
So at every point in time they always need to have a common ground and agree on things that come up because life is unpredictable, we only have to continue adapting.
Also when the change in agreement does not suit any of the individual involved, you may choose to fight for it(reasonably) or cancel the contract. it's not a do or die, but maybe in some cases tho which I may not be aware of.