Choosing a contractor according to the lowest price, is like a fox guarding the hen house. Having a poorly designed plan by an architect or even a draftsman only increases tensions and creating an adversarial relationship between the owner and the builder.
O the builder will do their “part” in the construction of the project, but won’t care that the project does/doesn’t get done time, or care to make the job flow for subcontractors on the job.
Remember this type of builder is already looking for another job, and yours is not even under way, it’s like a notch in his belt that he landed your job.
This type of builder doesn’t care the whys, where’s, who’s, when and/or for what purpose this project is even being done, he doesn’t have your vision or feel as to what you want to achieve.
Think about who you are aliening yourself with the relationship you start up now shall be set forth into the future for 10+ years.
You don’t know the building industry that is why you hired a contractor.
If you only pay the minimum remember that is all he himself has always done the minimum of studying in the industry and his work will show it.