Since I don't have much of a life, I recently spent an afternoon prowling around my saved cities trying to determine how much taxes the various levels of housing paid. Here is what I came up with:
The numbers in the right hand column show the total amount of taxes collected during one game year. The following conditions applied:
TRM = Tax rate multiplier as shown in column 20, Pharaoh_Model_Normal
It appears that the basic tax rate is approx .5 debens/year, and that the taxes are calculated roughly as follows:
(population) * (TRM)*(.5)
This does not come out exactly. Using this formula for a palatial estate, the taxes would be 1600. The actual number was 1584. There is a similiar deviation in other levels of housing. I'll leave it to the real bean counters to figure that one out.
What interests me about all this, is the realization that even a few crude huts pay enough taxes to justify the cost of a tax collector.
With the basic wage at 30, the six tax employees would cost 6 x 30 / 10 = 18 debens / year. The tax income from nine crude huts would cover this.
Paying for, and building a palace is another matter, but if it's already in place, or affordable, then I see no reason, short of manpower considerations, to hold off providing tax collectors much sooner than I have been.
Also notice the huge benefits in feeding your folks:
Common Shanty's pay taxes of 5 debens / year. Provide food and they evolve to Rough Cottages which pay a tax of 13 debens / year - Almost 300% increase!!
Another good move seems to be supplying beer to your citizens. The resultant evolvement of housing from Spacious Homestead to Modest Apartment increases the TRM from 2 to 3, and this results a significant increase in tax income. (17 debens - 27 debens)