Hello, I've started and invested in numerous B2B SaaS companies and YES, you should definitely try to sell first.

You must become the expert of your customer's problem (and the economical value of solving it) not of a product.

Most of the time, entrepreneurs tell me that it's a crazy strategy because 'what will happen if I sign??'. Very easy, you will rush to build the perfect product for your client! Clear roadmap, clear vision, no money lost. And you know what? If it takes too long, just say sorry to your client. He'll be upset, but it's better than upsetting your investor ... Or worse, your wife or husband because you've just lost the hard earned money of the family ;)

Don't hesitate to call to follow-up on this & good luck!