In all things be pragmatic. It is never wise for instance to trust anyone for any reason with your car unless they are perhaps a member of your immediate family. Never loan any money you expect to get back.
Many very serene people believe there is a law in the Universe. Karma if you will. A great teacher taught that what you sow, you will reap. Cast your bread upon the waters, and it will return to you. If you want to live in a world of trustworthy individuals, first become trustworthy in every area of your life, all the time to the best of your ability. The Universe will provide trustworthy individuals naturally, effortlessly.
Anytime I have centered myself in the will of a Power greater than myself, and got busy; rolled up my sleeves, got my hands dirty and helped anyone that was placed in my path that needed help, I had little or no time to worry about if they were trustworthy, and in fact, went to bed that night in the joy of knowing all my needs that day had been met. Peace. Enjoy the journey.