It's not unusual at all. If you do outsource, try and make sure you have a project lead that you can trust. Once revenues get up to a certain point they might want to see the project through and come on board full time OR they will have enough pride in their work to make sure a proper transition takes place.

As far as security, make sure you have an airtight non-disclosure/non-compete agreement with a penalty clause that includes financial remuneration.