Is it customary for collaborators to request NDAs without a formal employment structure or potential investment?
Yes.
There are some terrible takes here. That are pretty much are the right take for early companies and outsiders, prospective employees and investors, not other businesses.
It is bog standard to sign a mutual NDA in situations like this. An NDA doesn’t suddenly mean you scream everything at the top of your lungs to them.
Yes you should be concerned about what your say to them. Like any relationship they need to prove trust.
This is likely them sizing up an acquirehire or a bigger partnership because they see you doing something they can’t do or aren’t doing well for whatever reason. Ask them!
9 out of 10 providers are trash and just advertise some basic thing that isn’t particularly hard to do internally.
Marketing is a critical function that is often outsourced. Outsource the specific details, not the overall picture. You know your product and market better than anyone.
If you’re absolutely flush with cash bring in a hitter for a launch consulting setup but an agency is almost always a waste of money at the early stage