It all depends on whether or not you're an unpublished writer. If you're new, the agents/production companies will jack you around a little. Most likely it will be anywhere around $25,000 to $50,000 for your first. However, if it's really good, it could be over $100,000. It just varies.
You sell your screenplay idea by pitching it. You pitch these ideas to producers, actors, writers, talent agents, managers or other people who can 'take the next step', which is to produce either a treatment or a screenplay. A treatment or screenplay can be copyrighted; an idea cannot.
A screenplay is a product. It tells a story. You can write the story as a pitch, as a treatment, as a novel or as a screenplay. Both are required in order to tell your story on film.
If you've written a screenplay, an agent can help you sell it. Selling it yourself may or may not be your strong suit.
Unless you make it a condition of your contract when you sell the screenplay, it won't be up to you. When Sylvester Stallone sold the screenplay for "Rocky" he required that he would play the role.
Bollywood screenplay writers get paid in lakhs . They do not get paid as much as actors. They certainly hold a lot of importance in the movies.
Once you have written, edited and copywrited your screenplay, you can safely sent it out into the world. Whether you would like to find a production company to make a film from the screenplay or an agent or manager to sell your screenplay, you must have a query letter. To write a basic query letter, include the title, logline and a short synopsis of your screenplay, and any relevant information about yourself in the letter. Then, start sending queries out to production companies, agents or managers to ask if they would be willing to read your screenplay.
Sylvester Stallone wrote the screenplay and would only sell it if he could play the role.
Write a screenplay.... Then shop it....
You can do anything you like after you write a screenplay.
Original Screenplay- Hannah and Her Sisters Adapted Screenplay- A Room with a View
Best Original Screenplay- Witness Best Adapted Screenplay- Out of Africa
Check out Zoetrope.com. Its primary purpose is for writers to workshop their works and Screenplays are scouted and optioned from that site.