The ProBlogger jobs board is your first port of call for writing jobs.
They have a huge community which they have been building up since 2004, and they are all about helping content writers turn professional and make money from blogging.
They also have tips, advice and tutorials that are all worth a look.
Contently is a great resource for content writers.
They have information about how to succeed at content writing, and they provide opportunities for freelancers to create content for them.
See their sister site Contently.net for further details on this. You just need to register wtih the platform, add some examples of great content you have written and then your application will be approved by one of the team.
Once approved, you are provided training and can start writing content for some of Contently’s top affiliated brands.