A tax invoice and a client with bad payment morale has left me in a pinch to earn a couple thousand EUR ASAP. What can a experienced Freelance Developer do to make some money quick?

Usually I would get another project but the only projects I was offered would start next month with earliest payment EOM. Which is too late.

The last couple of years I worked as fullstack developer with Rails/Ruby, Spring/Java, Kubernetes and associated technologies for German companies. In the past I also worked with C# & PHP and probably could get back to speed.

I would be able to live and breathe a project for the next couple of weeks the issue is how to find such a project quickly? Do you guys know clever alternatives like writing technical articles for blogs or something?

Thanks for your time and effort!