Secureview will only sell you are large quantity of boards. So if you are just starting in P&P you either have to spend big money upfront and keep asking your company to send you board up jobs or buy one board from a place like invisiboard and make pennies per job. I think invisi board wants to sell in bulk more.
It is much more expensive but looks better in the neighborhood. The 8x4 plywood might cost you $30 or less and can easily be found while the plexi glass is not easily found at any home depot and will cost $100 or better. Of course companies pay more for plexiglass however.