In MTW, you could only get trade income through trade w/other factions.. this was slightly absurd, as unless your government controlled all aspects of the economy- socialism, in a sense- then you would be getting your money off of TAXES, hence the income for trade between your cities would be most of what you were getting the income from!

Is it similar to MTW in RTW, or does trade between your cities net the same income as trade between your cities and the cities of other factions?

It seems the trade fleet paths generally lead to from one of your cities to another of yours!