The time it takes to develop a website can range from a couple weeks to several months. Obviously the more that needs to be done the longer it will take.
For example, if all you need is a one page website that displays information about your business and how to get in contact, this may take a couple of weeks or less. A website that has a thousand products that need to be entered, have pictures taken and organized could take several months to complete.
The best way to know for your particular needs is to let me know what you goals are then I can give you a ballpark on the time to develop.