Did some testing yesterday.
Without hindering my gameplay, I got to Level 12 (you can only make a guild at lvl12) with ~5g
Guild costs 10g to make.
Gold income increases exponentially so I guess I can get 10g at the point that the game send me to the city.
Another point: Guild Banners.
I'd love to find a way to be able to create guild banners in a way that people could see them and decide on one before making the guild (It's me that will have to create it since it was me that reserved it. Not that well thought).
This ones are the ones I made for beta:
I like specially the Dominion one there. The Icon is called "Conspiracy Theory" and sounded fitting for a comunity created in TSW
The shield behind it was just one of the choices for something that looked rather good with the icon.
There's a guy creating a list of all possible banners. It's a 3190 image load page, so it takes FOREVER!! It is still not complete but can give you some ideas of the icons and backgrounds (you can see all icons already since it's organized by backgrounds).
Warning: High load time and High bandwidth consumption - http://geekwagon.net/projects/WSbanners/