I got a question on Reddit a few days ago about what red flags I noticed as a freelance full-stack developer in NYC for about 7 years. There a quite a few so I decided to make a youtube playlist out of it. In the first video, I describe a common scenario where the founder(s) have all these grand plans and visions but absolutely nothing else - no name, no logo, no landing page, no FB/Twitter/IG/etc accounts, no blog - nothing. I see this as a red flag because everything I just listed requires no technical sophistication at all. A high school kid can do all that and several thousand, in fact, do.
Clients like this are walking straight into the trap that IndieHackers users know all too well - they will build build build without any validation and after several months and thousands of dollars later, we all know what happens.
The video covers much more layers to this if anyone is interested:
https://www.youtube.com/watch?v=ZSzWD3RLRxY.
It is the first of many more to come because in over 7 years, I have seen enough to write a book.