The investment may be contingent on obtaining the E2 visa.
The E2 visa is based upon treaty, so be sure you are from a qualifying country.
It is not an immigrant visa, but will allow you to work and travel.
It needs to be renewed every two years, but there is no limit to how often it can be renewed.
Your spouse can obtain employment authorization.
You can apply for this visa at an American Consulate in your home country without filing an application with USCIS.
How much is enough?
Although the regulations use the term "substantial" in describing the amount needed to be invested, $25,000 may be enough depending on the business proposed.
What is the most important first step?
Once you have established that you are from a qualifying country and have enough money to invest, you need to draft a business plan. You need not be an expert or have a degree, but you should have some experience relevant to the proposed business. A used car lot or ski rental shop can work if you can show how you plan to operate the business.
Something to be careful of.
You must be seeking to enter the United States solely to develop and direct the investment enterprise. This is established by showing at least 50% ownership of the enterprise or possession of operational control through a managerial position or other corporate device.