My Husband Wants to Start a Startup in a Few Months –I'm pretty worried. What should I expect? I will not promote

My husband and I recently got our green cards. He’s passionate about AI, infrastructure, & automation stuff and wants to start a startup in that space. When I ask him how he plans to do it, he doesn’t give me a concrete answer. His plan is to quit his job in July, speak to investors, and figure things out from there. He says he’s currently restricted from pursuing it due to work policies, which I believe is true—but I also feel like having a solid plan ahead of time would be better. I was on an H-4 visa while my husband was on an H-1B (SDE 3) on FAANG for about three years. I just received my employment authorization card, so I can now legally work, though I haven’t started yet. Over the past few years, I’ve been focused on fixing up our house after we bought a fixer-upper, so I don’t have much work experience beyond that. Financially, we have some savings and investments, but I plan to start working in May or June to secure health insurance and provide extra financial stability(although it's nowhere comparable to my husband's salary.) My husband seems like a smart guy. his performance reviews are always top-tier—but I believe that being a good software engineer and running a business are two different things. I have no clue what to expect from this, and we don’t have anyone in our circle who has done this before. For those of you who’ve been through the early stages of a startup, what were the biggest challenges you faced? What's the worst thing that we can ever face? What should I prepare for? My husband is super chill and thinks I’m overthinking, but I just want to be realistic because we'll only eat up our savings from this point on even when I'm working full time. It's quite stressful for me to step into unknown territory & fiancial troubles, but I support his decision and will stand by him no matter what. I just need to have my mind prepped ahead. Thanks in advance for your advice..!