1. Build leather tanner
2. Destroy leather tanner
3. Repeat steps 1 & 2

This is considered an exploit so if you're in to RPing don't do it.

Hiring swordsmen does not count toward the guild.

You can get SS's guild in cities. I got one in Genoa after building a ton of Urban Militia. When you consider you can also build Christian Guard from cities it's wise to leave the guild there.