[drenvuk]

MVP or fake page with credit card info or email information that says you're sold out.

If you can convert random users to paying customers then you're on to something. Otherwise your project is most likely going to flounder. Some people may think it's dishonest but without verifying you're going to spend weeks to months working on something that will never be used.

[coder543]

That might work for physical product, but when you claim your software download is sold out, people tend to give you funny looks.

You can definitely put up a product page where users can enter an email address and start building up a mailing list, but obviously mailing list recipients are not guaranteed to pay you money.

[drenvuk]

The purpose is to get some kind of signal that you're on the right track. Many times I've seen would be founders just go off of a hunch without a buy in from any possible users of any degree. Even their voluntary email sign up is far more of a sign than what the founders know users want.