It's a hard nut to crack. The 3rd party developers should be a good choice to hire for start-ups when no CTO on board or they are in short of  on-site developers.

On the other hand, outsourcing is not that easy. A huge number of outsourcing companies all over the world and though they are mobile application developers, they all do it in a various way.

You can use a short checklist below to decide your best outsourcing partner.

You want a “company,” not a factory: What to seek for bases on your project’s scope. If you’re an entrepreneur and want to build a new venture, you should find a full team that will be able to totally deal with your needs with 100% attention. Because they have time to commit to your product not only in development level but also personal. It brings the feelings like you’re working with human, not just robots coding for you.

Reviews and References: You know who you’re dealing with. There are some review sites to take a look at. You can get an overview about them and read reviews by their customers. Their rates and completed projects are also help you check it out.

Technology Stack: Ideally, you want to work with companies of “polyglot” developers. Who? These are software engineers who know multiple programming languages and can quickly learn new languages. Why is it important? Because every problem should be approached in a various way under different opinions. Companies which only uses one technology will approach issues from their tech stack’s perspective, sometimes may result in poor development techniques.

Talk with leaders. Talk with people: Want to know everything  about people you’ll be working with for the next X months or years. Know more about the leaders. Who? Are they experienced in leading teams and software development generally? Talk more with everybody related to your project to get to know them better because those people will be a piece of your life for a while.

Open Source: Check out Open Source companies and their GitHub and Bitbucket accounts. This helps you know if they are experts in code and software development. Also, you can check their creativeness.

Culture Harmony: Are they cool? Do you feel comfortable talking to them? Seriously. Make sure you will enjoy communicating with them because you’ll spend a lot of time with them.

Location: Time zone is an important element out of a good command of English and general skills of developers.