Population size needed for thief guild?

[garhkal]

One of my players is thinkin in the long term about once the party has fully cleared out the island, setting up a thief guild of sorts. BUT how big of a town/city would he realistically need for an 'average' size thief guild?

I know in the thief handbook, a village/town up to 500 folks, can by their chart, support up to 3 thieves, all the way up to a 5,000 person town, supporting up to 15 thieves.. With the average # of thieves a CHARACTER gets for followers, as being 14 (4d6 averages to 14), but as much as 24, do you think he'd need more of 10,000 civilians to support that number??

HOW MUCH land would a town of 10k, need to FEED them all? Based on some sites, an average MEDIEVAL size family, would take 28 or so acres to support themselves, (average being 2 adults 3 kids)..

[McDeath]

God, I wonder if that was covered in the Thieves Guild RPG products. I need to find those or at least a pdf.