You mentioned that you write articles, so if you create an article writing gig or two on Fiverr and include an even half-way descent sample of your 'good writing' you're sure to make $50 (...and probably more) in a day or two.
You can try working on online working platform like odesk.com. Some people are looking for small and quick tasks to be done you can earn there. That's the fastest way you can earn if you need it right away. You can also join affiliate programs and promote it so you can earn that 50 you want.
The quickest way to make $50 would be find a local business owner that' s in the service business and don't have a website and offer to build one for $100 dollars. That would be the quickest way. Or I see that you do voice over, then if you know how to create a video then create 10 30 sec video for local business and charge them $25 dollars or $50 promoting their business.