If you are outsourcing your software development you must think about the ownership of the code. Every country has it's own legislation about this, but often the ownership defaults to the author by means of copyright laws, hence the contractor. This is not good for a customer. We always advice our customers about this and actively encourage other arrangements. Depending on the situation, this can be shared code ownership or total code ownership, often combined with an escrow arrangement.
That's that then. You have it all on paper? You own the code? Good. But what if you end up in a situation where your contractor goes bankrupt, or is sold to another party. It might take you weeks to get your hands on the code or even worse... you might never even get it.
You want to prevent situations like this by continuously exercising your rights on the code. How can you do this? There are several ways to do this, but it comes down to the point where you continuously want the contractor to actively push all the code to you. Not at the end of a project phase, not when the next bill is paid, not even at the end of the current sprint. Most code is in a version control system, you can easily set up an automatic sync to a location you own. If you don't know how to do it, ask another contractor to be your conscience and set this up for you. You can even take it a step further from there and also verify the architecture, the code quality, etc.. for even greater peace of mind.
If you don't do this today, start doing it. It's so easy that it's not worth the risk.