Here are my thoughts about it:
I think, due diligence in this stage should be more about the founder historic and motivations than company matters. Of course start-ups loose money, “that`s why techs they are made for”, they are made to tracionate, gain scale and makert, and in this path, investing a lot of money with no gain. Techs start-ups are made to be next Google, Facebook or Uber, they are made to grow.
As I already said, it should be more about founder motivations, skills and historic, because only a good founder will lead a company to the success. Beware with contingents liabilities around the person of the founder, they could reflect strongly in the company future, and should be assessed. Skills should be assessed to, and encouraged to focus on new knowledge that would aggregate to company. Motivations and Objectives are one of the most importante aspects of the founder that should be assessed, having in mind that start-ups should grow and gain market very fast, or they are fated to death.