Trust? The one thing that we all lack but need

Just to share something about trust. To cut it short, i have lend out some money to a stranger. Well, it is not exactly a stranger, the person who ask to borrow the money is a janitor in the company which we never cross path. The amount is not big, which is reasonable for me to borrow it. The reason why the money is needed is not important as they could always lie to make you borrow them.

What i want to share here is more of a reflection of my thinking in the world.

What is trust
firm belief in the reliability, truth, ability, or strength of someone or something.
"relations have to be built on trust"

Above is the explanation by the dictionary. But how is trust being built in the first place? In order for a person to belief in someone, that means he/she must demonstrate some quality to create the trust right?

Based on this, it seems like it is merely an exchange of something between two people. For eg: If a really rich guy come and ask you to join an investment, you will most likely think about it. But if a poor guy approach to you on the idea, it's just nature that you think it is some sort of scam. Well, this seems like trust is not something that you can relied on if there is an apocalypse.

In the world, everyone is so connected and disconnected at the same time. Do we ever trust someone? As trust is earn, does that means that it is just an exchange of a something to get on the trust?