Pros: Community (always good to connect with other founders), some value in "brand" of parent company (if it's Google), PR opportunities, opportunities to network with folks in Google
Cons: No equity --> no stake --> limited incentive for the accelerator to provide you with tailored advice/mentorship, can be very time-consuming (and that's time you could be spending on your product), the "one size fits all" approach can lead to bad advice
Overall, I still think pros > cons, so long as the time is manageable. I think it would be great to have a Google stamp and meet other founders in the same space. I would also look into what the program commitments are (i.e. can you miss out on program talks/sessions without consequences?)
There is a question of risk allocation: if you hold unvested equity, you probably aren't paying taxes on it until it vests or you exercise it (depending on the equity), so would USCIS (who issues visas) know if you are working part-time if there's no cash component? I don't know. But the risk is really high for you and the startup bc if the government does find out that you're violating your visa rules, they can deport you (potentially permanently) and also subject the startup to consequences.
If you are really excited about the startup, it's probably not a bad idea to check with an immigration lawyer about your options (this is something that they could probably answer quickly in a free consult).
However, I don't want to transfer my work to someone else before I have seen any outcomes so that's my dilemma.
If you are very early-stage and not collecting sensitive data, one place to start is looking at the TOS & Privacy Policies at similar companies. While you should not copy these exactly (which could trigger a claim of copyright infrigement), you can make changes that make sense for your business. If you are collecting sensitive data (financial info, SSN, etc.), then you may want to engage a lawyer, especially if you are in California.