Fuck all the haters. Everything is viable. It is all a matter of angling it.
What will differentiate you? What segments are you targeting? .
Translating for affiliate marketeers might not be the best, since we don't care too much about authority (your degree), only the results. Many people speak Spanish, so you'd be competing with native speakers. Mucha gente sabe hablar y escribir en español, eso no te ayuda a tener una ventaja competitiva
But not everyone has a masters. You want to find something where your authority on the matter (your degree) will be valued and people will pay a premium for that authority. You want something where you can be the 'go to' expert for Spanish translations.
Maybe speazialize in legal document translations and find attorney clients? Or maybe become a notary and notarize translations of documents for immigrants? Maybe become a contract translator for import/exporters? How about your target major corporations and provide a 'Guarantee of Accuracy for $10,000 worth of damages" so you can target high level translations where they need to maintain a high degree of accuracy? Or maybe charge a monthly retainer for 24/7 access to a translator for businessmen who regularly need an on-demand translations?
If you jump in with all the rest, you are competing with them all and the laws of the market (supply/demand) will make it so you can only charge so much. Find a niche and dominate it, and you can charge very high premiums for your expertize.
If you want to do mass translations for niches where you can't extract a high premium, you will need to set up a highly scalable high-volume, low margin business model (think textbroker) But I don't think that is what you want (or are ready to start either)