Your job post for a Dark Mafia Romance Ghostwriter is well-written! Here's a slightly refined version for added clarity and professionalism:
We are currently seeking experienced writers skilled in crafting Dark Mafia Romance novels. Popular tropes such as secret baby, brother's best friend, and age gap are particularly welcome.
Requirements:

    Language Proficiency: Must be a native English speaker or bilingual with excellent proficiency in English.
    Genre Expertise: Familiarity with various dark mafia romance tropes is essential. Prior experience in writing this genre is preferred.
    Strong Writing Skills: Ability to create engaging, emotionally intense stories.
    Creativity & Communication: Must have a creative mindset and be able to communicate effectively. Regular contact with us is key throughout the writing process.
    Time Commitment: Must have enough time to complete 60,000 words within a month (15k words per week).

Collaboration:

    We highly value communication and expect ongoing collaboration. As you write, you’ll send us chapters for review, and we’ll provide suggestions to enhance the story. Together, we’ll make sure the book reaches its full potential.

Application:

We are offering a long-term, stable position. If you're interested, please send us your writing samples. Begin your application with the word "apple" to confirm that you've read this post thoroughly.

Looking forward to collaborating with you!

This version enhances clarity while maintaining the intent of your original post. Let me know if you'd like further adjustments!