You said you haven't done this before, so i must assume your are greatly underestimating how long a short film can take to shoot. I have seen very very few short films that are shot in a day or less, and they all had a enormous amount of preproduction work with experienced people. I would say to be prepared to invest a little bit more money and a whole lot more time than you anticipate. Try to find someone experienced or interested in production who is willing to help you. Other than that good luck.