[jaxn]

I am about two years in to something similar. resaleAI.com

Don't worry about keeping the vertical secret for competitive reasons. You either have the domain expertise to make it great or you don't. And anyone with the domain knowledge knows what they want, but likely don't have the tech skills to make it happen. If you have both, start with the tools you know and get going.

I went the web/bootstrap path for most of it. I'll do mobile apps this year.

Get customers first. I had customers before the project had a name LR a signup form or much of anything.

Got fast.