How Translation Rights Work
When you sign a publishing contract, translation rights are either retained by you (in which case you can sell them separately) or licensed to your publisher (in which case they sell them and share the proceeds). If you self-publish, you retain all rights by default. If you are traditionally published, examine your contract: many authors do not realize they have retained translation rights because they did not read the rights schedule carefully. Knowing what you own is the first step. The second step is knowing which markets are realistic for your book.