[mooreds]

As little as possible if it is a true MVP. The goal is to test the business idea.

If possible Google forms plus shlepping.

[siquick]

This^^

As long as you're solving their problem, the vast majority people don't care how you're doing it.

[maxxxxx]

I think that's the way to go. From the outside it looks like the real thing but internally it's the bare minimum. But you have to be ready to scale up quickly if needed.

[mooreds]

I think, based on experience and reading, that "being ready to scale up" is nice but you'd be surprised at how much you can do with email.