For what purpose will the machines be used? Unless there is a VERY good reason why off the shelf wont work then I highly recommend buying from a vendor that specializes in business laptops (Dell, HP, Lenovo, etc).
The cost of supporting homemade machines for business use is going to be well beyond reasonable. Lifecycle, driver support, bug fixes, hardware warranty, etc. I do not see a win in building custom laptops unless there is something specific about your needs that would absolutely require it.
Or are you talking about making a business that SELLS custom made laptops? In that regard you aren't going to make any money until you reach sales in large volumes. Or, you can find a niche market that can be exploited.