From experience, even if you are within your competency to complete the task yourself but simply want to speed up the time it takes to hit the market, you should still expect to spend a good amount of money to get the job done.
Keep in mind that you need to define your terms well with your contractors (be it in China or India), because as soon as they spot your weakness, they will try to raise up the price (like a smart business man would do).
From experience with negotiating with firms in India, my impression is that you need to at least hire a development lead in U.S. or within your proximity to monitor and help bring the project to completion. The contractors will often throw at you with their agile approach, which is nice, but it is also another way of saying "we don't know when this will be complete, because the requirement can change. Maybe it will take 3 months or more to complete, and by the way, we offer additional service if you go on hourly rate etc."
From outsourcing firms' perspective, it is just a contracted job to them, so code quality and unit tests aren't really their top priority. And worst of all, they may reject having your development lead involved in the assigned project. So by merely making clear demands early on, their response can be either positive or keep delaying until they drop out of the bidding all together.
At least in Texas (U.S.), we aren't legally allowed to hire foreign workers with hourly wage. We are, however, legally allowed to purchase a fixed cost solution. That often does not sit well with most firms that prefer hourly wage in agile development. So make sure your outsource needs meets the tax code in your country.
Lastly, especially if they know you need them, they will demand a 20% to 30% down payment. That is really only fine if they have a division or an established office within your country (i.e. U.S.A.). If not, you are truly at the mercy of their professionalism.
All these are my experience and my personal view, so yes your mileage may vary. It is not a horror story meant to scare you, but you need to be aware of all the trade-offs before spending the next 2 months sourcing a good contractor