I wanted to purchase a feature length script to produce and direct myself, and have been looking around, but so far, I haven't found a script that really pops out. How do other filmmakers tell which scripts are worth making, compared to not, if they just have one shot?
Also, just because you think it's good or bad, does not mean other audiences would. So how does one go about accessing it? Do you just say I like it, let's buy it, and make a movie, and that's it? Especially because it can be hard to get good feedback from many people, in such a small window you have to buy the script, before anyone else does. Does anyone have any advice?
Thanks

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What is your goal in making the film? If it's to make money, then you need to select a script that has market potential. If your goal is to make a festival film, then identify festivals and be sure you're clear what kind of films they normally show. If the goal is to master skills, then you will want a script that has not only a variety of shots but is well in budget. Now obviously a combination of the above is possible, but initially it's best to have one in mind.
A producer should have a solid grasp of budgeting a film. If you feel unsure, then you need to educate yourself. I usually anticipate a minimum of $300 per 12 hr day for a No/Lo budget. Now script filming can vary widely depending on content. However for an average, 1 page = 2.5 hrs to shoot for 1 minute of screen time. Obviously dialogue heavy scripts are shorter and action sequences can be longer. For a well balanced script, say of 100 pages, you have about 250 shoot hrs or about $6250 for a 1.5 hr film that takes about 12 weekends to shoot (about 2.5 months). That is a base and doesn't include props, permits, costumes, etc. which are story dependent. You will need to feed your cast and crew, have production expenses (batteries, memory, etc.) and miscellaneous expenses (printing scripts, etc.). Now, anticipate about half again for post, marketing and distribution. So for your film, you should anticipate at least $9375. This doesn't include your script purchase.
Everyone has their own numbers from personal experience so I'm not suggesting this is exact for everyone. It will depend on your location/country, what other resources you can draw upon, etc. When considering scripts, you need to keep in the back of your mind, that regardless of the story, you will need about $9500 for a feature indie film or about $95 per page. I'm not talking about shorts or student projects. This is where you need to acquire, rent or find people with film equipment. There is also a "corollary" that the cost factor can grow or shrink with the film size. A 30 page script may only cost $60 per page while a 120 page script can cost $120 per page. As a producer, you need to keep budget in mind. Go back over your past films and identify where you went over budget and why. Use that to make better estimates.
Again, what's the end goal? You say your audience. Who and where is your audience? Is distribution for theatrical release, direct to DVD or streaming? How do you intend to market it? Will you go the crowdfunding route? Do you have a social media campaign in place? Each service has costs associated. A good producer is worth their weight in gold. You can do it yourself but it helps to network with other filmmakers in your area who can help guide you and assist with finding resources.
Choose a script that interests you as a director. Once you purchase it, you can make changes to it. You're not tied to the script. There have been other threads detailing this about options and purchases. Props, costumes and effects add up quickly. If actors can provide their own, that's a plus. So contemporary settings are much more appealing. Fewer actors make scheduling easier. Identifying scripts is a balancing act. I may see what films are similar, what the budgets and returns were. I may ball park a rough below the line (BTL) estimate. The above the line (ATL) costs (salaries for actors, directors, producers, writers) is typically about 3 to 4 times the BTL in major union productions. Though the BTL estimate given union crew would also raise the per page estimate. In-house studios often have dedicated crew so that balances out. So a 1.5 hour indie feature could run about $25K when said and done if you reach out to name talent (though not necessarily union).
So returning once again, your goal is to decide if the script you're reading can pull in enough views to pay off it's production. If this is a business model, you want a profit. As Rayw would say, you go where the money is and write/produce to your budget. If this is for personal education or festival, you might simply want to break even. If you can profit from it later, all the better.
As Rik said, if you feel strongly about it, option it. See what you can drum up for financing, working up the budget, etc. Once optioned, you can request a re-write. However, if you don't purchase it at the end of your option, you lose all rights to script and its re-write. If the script "speaks to you" and you're the director, it doesn't matter about the audience because you're making the film in your vision and inviting the audience to see the story as you do. Directors focus on telling an awesome visual narrative around the script. Producers can and often have to rein in talents to stay on budget and on schedule. It requires tact and diplomacy so again a good producer is golden.
A script that is well balanced, with a solid story that can be shot on budget should be the first criterion. Second, do you like it enough to invest your time and money ($10-25K for 5 months) to make this film? Lastly, do you have the skills and resources to pull it off? If the answer is yes to all, then consider optioning it. Use that window to do your pre-production work. If you cannot decide on the first criterion, get someone who can. Not lots of someones, just ONE someone and accept the pass/approve decision. No second guessing. It's easier to do that when it's not your script on the chopping block.
Once purchased, the script is yours to craft or re-craft. Story is only relevant to you as a director for how you want to make it come alive from script to screen. Remember, despite a good script, bad direction, bad acting, bad production quality and bad marketing/distribution can play into the failure of a film. That cannot be attributed to the purchased script.