Every set of custom house plans includes several items which need to be blown up and detailed for further clarification. If a set of plans does not provide additional close-up drawings (for things such as beam connections, deck railings, stairway construction, etc.), then it is not a complete set. It is very easy to cut corners during the planning process. But the end result will be higher costs for the home owner - and lots of frustration for the building contractor.
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.
Reproducible Set - You can buy a reproducible set if you think you may need minor changes made to your home plans. You can make copies from this type of home plan, but you are not allowed to build more than one home from these type of plans without a separate license.
On the other hand, stock house plans are substantial past drawn designs by a skilled designer or architect ideally of a specific purpose or general use. The question is, why choose a stock plan over a custom drawn plan? It all amounts to various reasons that are discussed below.