One item to look for when evaluating a house plans' quality level is the number of structural sections which are shown on the plan. Highly detailed sets of plans will always cut lots of sectional views through the house to show every different roof framing situation. This might mean that 10 or 12 (or even more) sections need to be drawn for a large house plan. And even a small house plan should include 3 or 4 sections minimum. However, many home plans available today (especially plans purchased through inexpensive plan directories) cut corners in this department and only show one or two house section views. This means that the builder will have to guess at the rest of the house framing.
The property owner can seek a variance to exceed the "building envelope," the allowable area that a home can occupy on a lot. However, the process is often lengthy and there's no guarantee that permission will be granted. Local zoning boards and community organizations often require a house be set back a certain distance from the street. Before purchasing a corner lot, find out if front-yard setback regulations apply to the lot's front and side-street boundaries. This could substantially reduce the area available for a home's footprint. Easements as well as natural features, like rock outcroppings and mature trees, may also influence where the house can be located.
In addition, good stock plans come with a detailed inventory, which you can use while you're developing out your dream house. This is important for two reasons: you can look at the materials used to build your house and determine whether your budget will stretch to accommodate them, and you can get a very good idea of where to upgrade and downgrade materials.
Another item which is often missing or lacking in a set of house plans is comprehensive and accurate dimensions. We have always strived to provide more than the minimum amount of house dimensions so that it is easy for the owner and builder to layout a home on its building site. We will even calculate point to point dimensions (using trigonometry) for homes which have lots of odd angles to them (as opposed to a simple rectangle layout). Not all architects or designers will go this "extra mile," so it pays to check these things out beforehand.