If you're going the outsourcing route there are a couple of things to know depending on the country you are in. Most "Sr. Level Developers" are people who have only 2 to 4 years developing. What's worked for me in the past is assembling my own team or finding a real Sr. Developer who's been doing it for 10+ years. This will greatly reduce your cost and your head ache. I lost $10K on a project learning this lesson.

In regards to the hosting of the app, Amazon AWS or Rackspace or even Digital Ocean are all great places to start as has been mentioned above.

One last thing, since you're in it deep, avoid making the mistake of pushing things out the door without testing. Get a test dev who's onshore to test your app before you push it out the door. It will greatly save you on the cost of support tickets.