Everyone has daydreamed about flying over traffic during rush hour. A couple months ago, I started looking into how that could be possible.

I was very excited when I discovered ultralight aviation, and that I could actually afford a Mosquito XEL helicopter in a couple years! (I'm in college)
Through I would mostly use it recreationally, I would like to be able to use it for transportation too when I could. But I'm not sure how the FAA works or the specifics of what I can and cannot do.

For one,
§ 103.15 Operations over congested areas.
No person may operate an ultralight vehicle over any congested area of a city, town, or settlement, or over any open air assembly of persons.

On another thread, someone wrote that "congested" is about 10 houses clustered together or a school. Do different districts have their own definition of what is "congested"? I found distances that one must be from a congested area in a fixed-wing aircraft, but there seems to be no limit for helicopters. "Helicopters may be operated at less than the minimums [...] if the operation is conducted without hazard to persons or property on the surface." So, how close is too close? Is 103.15 a moot point so long as I prevent violation of § 91.13 Careless or reckless operation.?

And what kind of fines could I expect if I was reported?

Particularly, how wise is it to land on water retention ponds or vacant lots? Is it ok to cross two-lane or four-lane bridges or highways (at higher altitudes)? What if I got the permission of the owner to land on their roof or property, but it's near a parking lot/residential area?

Thanks!