I am founder and CTO of a startup, and I have hired and grown a few teams. Contact me directly at cto @ nosql dot com.
Some general advice: It is ok to hire individuals remotely, but do not start with time and materials. Pay for work product. Get a lot of quotes and hire multiple people and keep the best Use the full SDLC tools to ensure quality: git, tests, stories, Ui mocks, etc It is ok to choose a cheap database or other core tech, but design the system to be able to change. Using the cloud will be faster and cheaper to start, but more expensive in the long run.
But longer term I've found that serious professionals tend to skew more to billing for time rather than per-project (I'm not saying there aren't exceptions), because they've at some stage come across scenarios where clients scope a huge project with them, and all the friction is backloaded towards the due-date as the client and team begin arguing about whether the spec is delivered or not.