I have started a small business based around a machine which can fabricate parts from a limited subset of material. I eventually want to get a larger machine which will remove the limitations but I simply don't have the cash (or credit) at this moment. So, I want to 'partner' with another local supplier in the meantime so that I can take orders for any materials from the start. For now, I will simply funnel the larger work to this supplier until I eventually have the funds to purchase my own machine.
My question is do I need any type of legal agreement with this supplier? There are requirements I'd have (quote turnaround time, maximum lead time, etc) and I am sure there are requirements he'd have. Where do I start?