How do you structure the deal when using a hard money lender? It's just like any other lender. You get prequalified with the hard money lender, they give you a letter saying you are qualified for a loan for X amount, and then you use that letter to make offers. The escrow/transaction is the same pretty much, except usually hard money lenders require less red tape and so they can close considerably faster than big box lenders most of the time.
Can a buy/hold property cash flow when using a hard money lender? Probably not. Hard money is used more often for flips. They charge high interest, prefer short amortization, and are very liberal in charging various fees. So, 99% of the time, no you can't cash flow with hard money on buy and hold. Just use cash or conventional financing for rentals, trust me.
Can I use a hard money lender to purchase more than 1 buy/hold property? Yeah, of course you can use the same lender for several purchases. They probably would want separate loans though, which means separate loan fees, separate down payments, etc so they can foreclose on separate properties in the event of default.