You can obviously outsource the technical development of your product / MVP. However beware that often this puts a glass ceiling on your company since no one cares enough for quality, scalability etc which become important if your startup is to take off. On the other hand, you're implying that the team in question would take your startup to Series A. That is a very different value proposition. If they are saying that they will take the company to Series A, I would be very skeptical since getting to a Series A round implies reaching some level of product/market fit and having a sound business model and therefore is a significantly wider proposition than simply building the technical implementation of your product.