Honestly I would never recommend an asynchronous online class for any foreign language over a live online or (even better) an in-person class. It doesn't matter if you're learning Spanish or Arabic, you've just gotta have regular live interaction to properly learn a new language.

Being able to speak Spanish greatly enhances your resume. If you are bilingual you are more competitive in the workplace. Whether as a Spanish teacher or that of any discipline, you can make a difference in the field of education. Your language skills will enable you to interact with English Language Learners.