E-2 Treaty Investors Visa

The short answer is no, there is no minimum dollar threshold to meet. Instead, the government will look at factors such as the proportion of the investment related to the total cost of the business, or whether the investment is typical of an amount required for a viable investment in an enterprise of that type.

The treaty investor or enterprise must notify USCIS by filing a new Form I-129 with fee and may simultaneously request an extension of stay for the treaty investor or affected employee.

The Form I-129 must include evidence to show that the treaty investor or affected employee continues to qualify for E-2 classification. An employer who no longer employs an E-2 nonimmigrant is urged to inform USCIS of this upon termination of the E-2 nonimmigrant’s employment.

Treaty investors and employees may be accompanied or followed by spouses and unmarried children who are under 21 years of age.

Investor / Employee may only work in the activity for which the immigrant was approved for at the time the classification was granted
USCIS must approve of any “substantive change” which is defined as a fundamental change in the employer’s basic characteristics that would affect the alien’s eligibility for E classification such as:
A merger
An acquisition
Sale of division where the alien is employed; or
Other event that affects the treaty investor or employee’s previously approved relationship with the treaty enterprise.The Marginality Requirement
When you first apply for an E2 visa, you are required to show that the E2 company will not be a marginal enterprise.
A marginal enterprise is basically a business that only generates enough income to provide a minimal living for the E2 investor and their family.
When you first apply for an E2 visa, you are required to show that the business will not be a marginal enterprise.
If the business is a start-up company, you generally show that the business will not be a marginal enterprise by providing a business plan with pro-forma future projections for how the business will perform.
When applying for an E2 visa renewal, you generally can no longer rely on future projections. At the point of E2 visa renewal, the business has likely been operational for multiple years. Therefore, at this stage, the actual performance of the business is the primary indication of whether or not the business is a marginal enterprise or now.
The immigration official reviewing your case will review the past performance of the business to determine whether the business is not a marginal enterprise. To satisfy this requirement, you should provide the business’s past financial statements. The financial statements should indicate that the business is generating more than enough revenue to support the E2 investor and their family. Alternatively, you should provide evidence that the E2 business employs workers as this can also be helpful to show that the business is not marginal. A combination of evidence showing revenue and job creation can also work to show that the business is not marginal.
If the E2 company’s revenues are minimal and/or the E2 company does not have employees, this poses a challenge when applying for E2 visa renewal. This is because the business is at risk of being considered a marginal enterprise. To overcome this hurdle, the applicant for an E2 visa renewal should provide credible evidence demonstrating how the business will improve to a point where it will no longer be marginal.
One way to show that the business will improve is to provide evidence that you have committed additional capital to the business with a plan in place for deploying that capital productively. An updated business plan should also be included to demonstrate how the capital will be used to improve the performance of the business.

Before the I94 expires

It depends. Everyone is different.
Routes
EB-1 “Alien of Extraordinary Ability”
EB-1 “Multi-manager or Executive”
Family Based

https://www.uscis.gov/i-129
https://www.uscis.gov/i-539
https://i94.cbp.dhs.gov/I94/#/home
https://www.uscis.gov/i-907
I-797, Notice of Action
Copy of Passport plus/including your E2 visa
Employer letter demonstrating why extension is required
Copies of personal and business tax returns (prior 2 years) plus payroll tax returns
Proof that you are physically present in the US
Applying for an E2 Visa Renewal at the Consulate
https://travel.state.gov/content/travel/en/us-visas/visa-information-resources/forms/ds-160-online-nonimmigrant-visa-application.html
Pay the DS-160 fee
Complete the DS-156E and organize supporting documentation
Present documentation illustrating that you still meet the requirements of the E2 Visa
Documentation and the order of the documentation that must be submitted varies depending on the consulate. Please check with the consulate where you will be applying for specific instructions.
Attend interview

The filing fees are subject to change. You should always consult USCIS’ website when submitting filing fees.
I-129 – $460
I-539 – $370
Biometric – $85
Premium Processing – $2,500

USCIS Link 
https://www.uscis.gov/working-in-the-united-states/temporary-workers/e-2-treaty-investors
For a list of treaty countries
https://travel.state.gov/content/travel/en/us-visas/visa-information-resources/fees/treaty.html