Don't Outsource. Period.

While there are big drawbacks with outsourcing related to building internal expertise the real reason I would never outsource at your stage is the need for speed and flexibility.

Per your description, you are an early stage start-up with a MVP that is gathering data. Congratulations as that is a big accomplishment! However, you inevitably have a ton to learn about what your prospective customers need most and what customers deserve your attention most.

The means you will be tweaking your product constantly for the foreseeable future and having to submit ideas to an outsourced team, make sure they understand what you want, wait for the new feature to be scheduled, etc is just too slow and too expensive.

You should have your developers literally sitting next to you and (if you have one besides yourself) your product person so you can quickly and constantly share information.

Good luck! You are in for a fun ride...