Planning to withdraw from a job offer for another

Hi everyone,

I recently accepted and signed an offer with a startup company that is based out of US (in San Francisco). Today is April 1st, 2016 and the job is not supposed to start until April 18th. And the company is in the process of creating a legal entity in HK but it is not in place yet. My understanding is that without the HK legal entity in place they won't be able to get the process started on applying for a HK work visa for me either, which is something I will need.

Long story short, the startup founders turn out to be a pushy bunch, demanding that I start working in advance without pay. And a lot of the long distance meeting phone calls that we have are out of my own pocket. They have promised to wire some cash up front but those promises have been broken each time.

As luck would have it, I recently received another offer with a large corporation. I would like to withdraw from the current offer I signed with the small startup, but would like to know whether there are any legal ramification for doing so?

Does anyone know?