Without know knowing about the infrastructure you will run it is difficult to answer. I would start by looking at the baseline for infrastructure, for example the web server software (IIS, Apache, Tomcat, etc) and databases (MySQL, MS SQL, etc) and go from there. 1000 visitors/day is going to be a light load but 1000/minute could be a relatively heavy load depending on the application.
If you are just starting out I would look at building an architecture that can build out and up as you grow. For example handling multiple front end servers, larger database servers, data caching/sharding, and other scaling techniques. This makes it less important to get the sizing exactly right from the start and will allow you to scale as needed.