@Angel23,
I think perhaps a part (maybe a big part) of this is that you're co-workers have experienced in the past the results of getting into conversations with you, and suddenly finding themselves in uncomfortable territory. So, they've learned just to avoid interactions altogether.
You mentioned in your posts you never ask about money. However, in the examples you gave, you do ask about money, both directly and indirectly.
If someone asked me how I could afford to take a cruise or vacation, I'd be pretty standoffish to you.
Someone works a 2nd job, most likely for extra money. It's really no ones business what she's doing to make it, or where. etc.
I'm trying to put myself in the place of the people you are asking these questions. I'm thinking of people who have come into my life that I thought were asking me uncomfortable questions.
A big thing I feel in my gut is that your questions to someone seem really random, catching people off guard. I know you want to be friendly, but it's probably better if you ask friendly, non-threatening questions about what you and the other person are directly doing with each other.