When installing an exterior door, don’t worry about using shims between the door frame and the rough opening for proper support. Three drywall screws on the hinge side only should be more than enough to attach the door into the opening. If not, the load-bearing ability of the exterior trim will suffice. When installing the header over the door, rather than sandwiching boards of the proper thickness to make a uniform piece the same depth as the opening, just fill the remaining void with a tube of clear caulk. That will make a great nailing surface for the exterior trim.
Additionally, rather than using expensive flashing and water-resistant building paper to form a proper drainage plane behind the siding, a whole tube of caulk between the brickmould and the vinyl J-channel should be good enough. After all, don’t all proper vinyl siding installations make use of lots of caulk?
Finally, when finishing the installation, why bother with insulation between the door and the opening – that’s what trim is for, right? When painting the trim, one coat of interior white paint should do the job. There’s no need to spend time with extra coats of primer. If, when removing the masking tape, some tape remains on the door, just leave it. I’m sure after ten years it will dissolve and fall off on its own anyway.
I hope these tips can be of value to you and help you cut costs to maintain your profits.
P.S. Perhaps the most frustrating thing is how much more effort I put into doing things the right way building my kids’ backyard playhouse compared to the work of these “professionals.”