I finished one of the "special" jobs from Delvin, but I'm still slogging through Vex's. I just checked, and apparently you have to finish 5 smaller jobs in each of the 4 major cities to get that city's "special" job, and then you have to finish those 4 jobs to become Guildmaster. That's a lot of sidequests, dammit. (You're right though, I'm flush with cash right now)