Professional writing software like Final Draft is not necessary when you’re just starting out. There are cheaper alternatives.
We used to recommend Celtx, but since going from free to a paid model and “browser only” interface, the reviews have been mixed.
A free, cloud based option is Amazon Storywriter. It seems like a stable, if bare bones solution.
Another freemium app is Writer Duet, with more features that unlock if you pay a subscription fee. Both Amazon Storywriter and Writer Duet are based on Fountain, a plain text markup language for screenwriting. For more Fountain-based programs, visit here.
With any cloud software, it’s important to back up your work to your home PC. Don’t rely on web apps to save your files forever!
Here’s a list of some paid software.