[quote]It would be like going to the restaurant with your own food and say cook it for me. [/quote]

Most people do cook their own food.

[quote]Like I said, you can build your own house too; and you don’t need a contractor’s license to work on your own property.[/quote]

Sadly, that’s not always true. For example, you can’t drill a well on your own property in CA (you need a specialized well driller contractor license, which costs ~$400).