A little caution is always wise.
Discussion
Me be cautious?
Yup. There are always going to be people who will try and take advantage of the kindness that you show them, as a means to benefit themselves. Life ain't no fairytale.
How should I be cautious?
Or just be cautious and aware that people do this?
The last one. The point I'm trying to make here is that finding good quality friends is a far more difficult task than people understand.