I found a great sysadmin on Craigslist ... I now pay a $600/mo retainer to have him on call up to 10 hours/month. I usually don't use all the hours, but sometimes I go over and pay more.
The situation works great for both of us.
I don't think Patrick's model is ideal for sysadmin work (who needs a sysadmin for an entire week?) ... but I think the retainer/on call model could be just as good ... get 10-15 companies paying $500/mo ...