Designing a home plan or finding a stock home plan is pretty much like buying anything else. Lets take purchasing a car for example. Probably the first consideration for most of us is the cost. Then we analyze our needs and wants and try to figure out what car will be the best bang for the buck.
- is it roomy enough? - is it attractive? can you see yourself driving the car? - does it have the features we need/want? - is it energy efficient? or do we make enough money that it isn't an issue?
The list can go on. Unfortunately you can't test drive a home, but if you buy a home from a home builder that has several projects under way, it's likely you would be able to preview some of his work to make sure it is what you expect.
Cars are a little different because they are designed to meet the needs of the average person. Home plans, when custom designed anyway, are often designed for a specific person. It is important to remember that you may not always have that home. Things change. Sometimes a guy has to sell his truck 'cause he needs a family car. I think it is important to choose a home plan or design one that meets your needs, but also meets the needs of the average person. One of the main differences between cars and homes is that homes maintain and often increase their value while most cars depreciate rapidly.
Professional designers are similar to the car companies. They deal with all aspects of home design regularly and as a result they most often produce plans that are a good representation of what the average person needs and wants. Of course they will do that... they want to design house plans that will sell.