It's important to catch one bus or another to start the journey. I, along with my company, have had worked with plethora entrepreneurs on similar engagement, acting a a virtual, yet actual, team for tons of activities. There is no harm in partnering up with professional individual/firm and get started. Just ensure to complete the initial formalities in a best possible manner to keep everyone on a same page since day one. You would like to pen down things like roles, responsibilities, expectations, exit, stock options, post investment valuation, etc.

Plan everything keeping series A at the back of mind.