My usual strategy works well here: Hire in @min wage, with a huge bonus linked to new subs.
Depending on the size of the company it might just make a great graduate / junior dev recruitment program. Take them on with a probationary period and watch how well they do with the sideline gig. If they turn the code to spaghetti within months then you probably don't want them working on the core business. The last one through the mill becomes supervisor for the next one.
The only potential issue with this strategy is damaging the brand name of the consulting company. I'm not entirely convinced that this is really an issue.