Should you incorporate a company from the start? Or is it ok to build the MVP first?

My friend and I want to build a startup together and following the lean startup methodology.

Should we spend time and money to incorporate the company and get paperwork in order prior to starting the business?

Or it is okay to defer those expenses until we have a MVP?

Get the barebones MVP launched first to validate your idea.

Legal paperwork can come right after that.

One downside to that approach is potential problems with the co-founder can arise after a successful MVP test.

A simple way to reduce chances of that happening... agree to equity structure in advance before even starting any work. While it won't be a legal contract, send an email to each other stating the terms so there is some sort of record of you both agreeing to the equity structure.