It was not a bulk job.  We only accepted a few at a time and I was willing to "take the risk" as we had provided service a few years ago and although they were very slow in paying they did eventually pay.  After having a discussion about this concern, the promise of better systems and turn time for payment was enough to take the work.  Nothing has changed though.  So perhaps if you receive a call or email from this company, I would ask for advance payment (like an escrow account) and then proceed with the work.  

All the best!