Parking North of Campus - Scam?

For years I have parked off of Alaska Street without any issue and without having to pay a dime. However, when I tried to park in that area on Saturday, there was a "locals" from the neighborhood in every vacant lot, side of the road, etc., attempting to charge for parking. I parked in one spot that had no markings at all indicating that I had to pay, but I then see this guy going around asking people for $15. I began walking off and his female assistant grabbed me and asked if I had paid. I told her that I didn't see anything indicating it was private property. She had little response other than telling me I had to pay. I was pretty sure that they had no right charging people to park there so I left the spot and moved to another location that was free. Don't think they could have me towed, but I didn't trust them not to do something to my car. I can't help but think that the locals are now trying to take advantage of people parking in that area.