Short films don't make money so you will be asking for donations. Typically the makers of short films finance then on their own. Are you asking how to get other people to pay for your movie? The key is understanding that you are asking people to give up money they worked hard for to pay your movie.
So have a plan. When you approach people give them your “business plan”. If you’re making a short that won’t see a profit then you will need to show them 6 items.
1) The format it’s being shot on
2) The line item budget.
3) What your plans are with the finished movie.
4) A short bio of the people involved.
5) The amount of days you will need to shoot and edit.
6) A copy of the script.
Since in this case you are asking people to invest because they believe in you and want to help - not for financial return - you have to make this very personal. Don’t make promises about getting into festivals - though do you research and tell them about the festivals you plan to enter and how much that’s going to coat. However, plan a showing of the final movie in a public place so everyone can see it.
Don’t try to dazzle them with how much money your movie is going to make unless you can back it up with facts. Example: how many short films similar to yours have turned a profit.
Sell yourself as as an up and coming, dedicated movie maker.
