Ask HN: What visa do foreign YC founders use to stay in US beyond 3 months?

Regardless of whether you're a YC founder or not, in general unless you're Canadian/Mexican and can qualify for a TN, or Australian and can qualify for an E-3, your only viable real option is an O-1 (Alien of Extraordinary ability). It's not an unachievable visa, and there are many founders who use it, but the requirements to demonstrate extraordinary ability are onerous.

From USCIS:

* Receipt of nationally or internationally recognized prizes or awards for excellence in the field of endeavor

* Membership in associations in the field for which classification is sought which require outstanding achievements, as judged by recognized national or international experts in the field

* Published material in professional or major trade publications, newspapers or other major media about the beneficiary and the beneficiary’s work in the field for which classification is sought

* Original scientific, scholarly, or business-related contributions of major significance in the field

* Authorship of scholarly articles in professional journals or other major media in the field for which classification is sought

* A high salary or other remuneration for services as evidenced by contracts or other reliable evidence

* Participation on a panel, or individually, as a judge of the work of others in the same or in a field of specialization allied to that field for which classification is sought

* Employment in a critical or essential capacity for organizations and establishments that have a distinguished reputation

Additional info on the O-1A can be found here: http://www.uscis.gov/working-united-states/temporary-workers...

I'm specifically ignoring H-1B as an option because it's only a viable option between April 1st and 5th of a given year, and the odds are very much stacked against you at this point (from a pure statistics perspective).

There are a few other visas that may be an option, such as the investor visa (E-2), and intra-company transfer visa (L-1), but these are highly situation specific visas.

Also, this is not legal advice, I'm not an immigration lawyer, and you really should talk to an immigration lawyer :)

If they are from a "treaty country"[1] they could apply for an E-2[2] investor Visa given that at least 50% of the company is owned by entities from the treaty country (easy at that stage) and you could demonstrate a substantial investment in the company (if you are after the prototype stage shouldn't be a problem for a good visa lawyer).

On your specific question, from feedback of my lawyer, if they have invested (read: spent) more than 100K in the company they are good to go. No requirement on how much you have raised (but obviously at least 100K).

So should't be a problem for a typical YC company.

[1] http://travel.state.gov/content/visas/en/fees/treaty.html

[2] http://www.uscis.gov/working-united-states/temporary-workers...

Are they from different countries?

I wrote a long guide about this a while back.

http://blog.sourcing.io/visa-guide

I was on this visa. You must have been running the business in your home country for at least one year, and you must continue to keep the business running in your home country while you are in the U.S. (The U.S. office is supposed to be a branch). You also need sufficient funds (at least $100K, but $150K is safer). However once you get it, you can renew it for up to seven years, and, unlike the E-2, it has a path to getting a green card