What is the minimum distance from property line water can be drained?
None that I know of in 'The Code', your Zoning is what determines specific buffers. However, the Rule Of Thumb around me says you can't discharge any water in the direction of your neighbor that would readily flow over the property line...no downspout extension legs directed at your neighbor.

In the few States I've worked it's all the same and I wouldn't doubt you're in the same boat. This includes no flow allowed over pavements and sidewalks and no curb nor sewer outlets. All water must be given the chance to absorb into your property.

Check with your Codes, Zoning, Buildings, Permits or Inspection Department (whatever yours is called).