B1 (business) visa is easiest to get and it allows you to do fundraising, which is what you officially do during YC process. It allows you to apply for 6 month

B1 (business) visa is easiest to get and it allows you to do fundraising, which is what you officially do during YC process. It allows you to apply for 6 month visit on the first entry to the US and then multiple re-entries until you'll get funding and find possibilities/time for a more useful visa, like J, E, O or H1B.