Thanks for the warm welcome and the fast reply
Moreover, thanks for the help!
You basically found what I needed; which was the simple old xml file. While I still might want to know how to adjust the values as given by the 'GC.getCivicInfo(eCivic).getCivicOptionType()))' part, I am content with setting the 'UPKEEP_POPULATION_OFFSET' to '0' and the 'UPKEEP_CITY_OFFSET' to '0'.
In your original post you mentioned why the offset numbers are important, and I agree with you. However, I am trying a universal one city challenge (i.e myself and the AI can only have one city) and the civic costs were practically non-existent. Combine this with no research costs (as I have changed the techs to be discoverable only by Great People, so there is a randomness to tech 'discovery' and techs actually feel like they are being discovered), and I was left with only unit costs to affect commerce (no maintenance costs either). Thus, commerce was pretty lame in this environment.
Once again, thanks for the help. I managed to find out how to do many other modifications by just researching these forums and analyzing and exploring the xml files, but I was lost on this one. Cheers