For you to apply for your green card while in the U.S., you need to be in the U.S. in a work visa status, not in a visitor status. Alternatively, you can get your green card outside the U.S. through a U.S. Consulate (known as an "immigrant visa") but that process would take longer 6-18 months (versus 6 months or less if filed in the U.S.). And your employment as a contractor (as well as your and wife's assets) can be used to meet the financial support requirements.