Typical monthly wage for a programmer / designer: $600 to $1000. (This varies a lot, so there is no actual upper/lower limit)
My expenses:
Apartment Rent + Utilities: $80
Internet (1 Mbps): $23
Food: $135
Transport (Bike): $20
Books: $75
Contrast this with RealGeek's comment to get an idea on how different the expenses could be, depending on the person and the spending nature.Also keep in mind that I am not married. I expect the expenses to shoot out of the ceiling after marriage. :)
EDIT: Less than 6 months ago I was trying to get a startup up and running and I was living off my savings. The lifestyle then was entirely different and the expenses were around one half of those given above.