ANSWER

The BPMN standard allows for multiple start and end events to be used at the same process level.  There a few reasons why the business analyst may use multiple start or end events, but caution must be used to avoid mistakes.

Multiple start and end events can help avoid confusing sequence flow overlaps and intersections within your process model that might otherwise look like a bowl of spaghetti.  By using multiple starts and ends you can make the model more readable.

Multiple start events are also used when the trigger for the events are different and when once triggered they initiate the process at different points (initiate different starting tasks).  Similarly multiple end events are used when they are at different states.

The risk of using multiple start or end events arises when naming them.  Multiple start events (or end events) that are named the same ARE the same.  They are just two visual representations of the same event within the model.  So, if you name two start events the same but have them initiate two different tasks, you’ve created an internal inconsistency within your model and ambiguity for the reader of the model.  Similarly, if you name two end events the same but have them result in two different end states, you’ve again created an internal inconsistency within your model.