Then unfortunately, an E-2 is possible for your partner if he owns 50% or more of the business, but not for you. For your friend, while the law only says, "substantial investment", for the E-2 visa they usually look for around $200,000 or more. This is because anything less is a weak case that could easily fail. And they will not approve a visa for a business that they think will easily fail and you would end up being out of status.
Usually attorneys do not take cases of E visas for less than a $200,000 investment because they do not want to risk losing the case and having an upset client because the client has to have the money already invested and at risk and if it is denied, they have to try to sell the business or something to try to recoup their investment. If your friend individually has around $200,000 or more to invest, he should be good to do.
Here is a link to the E-2 if you want to read more:
If you own a business outside of the U.S. for more than 1 year and will continue to run that business, you can invest $100,000 or more in a U.S. business (doesn't have to be the same business, but must be related by ownership and here is where you may be able to partner with your friend) and you can try for an L-1A visa. Here is a link to that, but keep in mind that both businesses have to be run and should be successful. You can't just come to the U.S. and forget about the business outside and let it die:
So basically, your friend gets the E-2 and you get the L-1A. Later on, that may lead into a green card for you under EB-1C:
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