They should be useable with normal plastic sheet (cut to size), either to create items to use directly, or to make moulds for plaster, chocolate, soap, etc. The size of the items you can mould is limited, but it would still be a great item for many jobs, such as moulding new clear canopies for model aircraft or space toys, once you have carved a master from balsa wood. Moulding from an existing item would likely run in to copyright issues, but for personal use only it may be OK.
I would say you should play around with one of these machines, and regard your first attempts at moulding as experiments, until you get the hang of things. Do not expect your first few attempts to turn out perfectly. If you want a home vac-forming machine for small jobs, these things are available. This is available in NZ at $190. Something else to save up for.
Mold Press by We R Memory Keepers - YouTube
Mold Press Vacuform Machine Review - YouTube
How to Vacuum Form Like a Pro | We R Mold Press Machine - YouTube
We R Memory Keepers Mold Press! How to get a great press tutorial:) - YouTube
Mold Press - We R Memory Keepers - Creativation 2020 - YouTube
Yours Sincerely,
Paul Adams from New Zealand