Someone who is lazy, lives off of welfare, and doesn't care enough about their lives to start using the money in a useful and productive way, and instead, wastes the money on cars, drugs, etc. The monkey part likely refers to dark skinned people. This term seems to be used solely to refer to citizens of the United States of America.
"Henri used his welfare money to buy more crack, what a Welfare Monkey."
12 step recovery jargon referring to someone new who talks about how great life is, now that they'resober. Usually meaning that the person is out of touch with reality.
The new guy seems pretty happy for a dude who has no job, no money and no family. He must be on a pink cloud.