First you have to complete the Cure for Vampirism mission, and talk to The 
Count, Janus Hassidor. When you talk to him, ask him about the "Reward" 
conversation option, but don't leave the conversation, and keep asking him about 
it. Every time you ask him about it you receive 1000 gold (or more depending on 
your level). Do this as many times as desired for unlimited gold. Note that a 
recent June patch has fixed this glitch.