I think patio11 give great advice. Pick one that your founding team is comfortable with but I have a few suggestions.

If you are going to bring in off shore guys/gals it will be hard to find them proficient in some of the newer dbs. So the learning curve and cost inefficiencies maybe create a lost of momentum (time) for you. If I were to build my framework from scratch I would probably still use MySQL for certain thing but definitely move to a NoSQL (mongodb/dynamodb).