Head Or Tail?

Near my office, there was a middle aged professional person. He was very friendly and appeared to be quite conservative.
He would come into the office flipping quarters with one of us. It was a game the southerners play sometimes. 
You take a quarter, flip it, cover it with your hand. You ask the other person which side he thinks the coin landed on. Head or tail?
If you guessed correctly you won, you took the quarter; if not, you did not have the quarter.
He did this with us quite often.
Other times, he would just come in for a short visit. I guess that he was taking a break from his work. 
He was self-employed.
We had known him for years.

One day, he came by asking about a property that we had listed. The property was not occupied. He said that he wanted to borrow the key so he could go look at the property by himself. Since we had known him for years, we loaned him the key. 
He brought the key back later, and said that it was not what he wanted.

A few days later, one of the Realtors from another company came and took the key to show the property.
Soon there was a phone call from the Realtor.
"Did you tell me the property was vacant?' she asked.
"Yes," I said.
"There were some people in the house." she said.
"I don't think anyone else is showing it," I replied.
"When I put the key into the lock and try to open the door, there was someone inside pulling on the door, not letting me in . . . "
"That is strange," I said. Wondering who could be in the house. If it was someone else showing the property, there was no reason for the other Realtor to bar the door.

The Realtor came back with the key.
She told me that she was curious and decided to find out who could be in the house.
Long story short, she waited in her car and when the person came out of the house, she tailed him. It turned out, it was our Neighbor!
He was having a rendezvous with someone there. Apparently he had made a copy of my key. 
I was pretty upset. But I decided that I would not confront him.

Of course, he did not dare go into the house again. He knew that we knew about the incident.

It takes all kinds, like we say! 

You cannot trust anyone!