The Murphy bed I managed to get (for free, second-hand) was too tall for the low ceilings downstairs. I grabbed my drill, bought a few hinges and made this...
1. Locate the studs on an interior wall
2. Build a deck-type structure wide enough to accommodate the box spring, mattress and frame
3. Attach the wood structure to the studs
4. Install heavy-duty hinges.
5. Add feet on the bed frame
You can make a fold-up bed with hinges on the side that isn’t a Murphy bed, but it’s prettier if you get a Murphy bed because it has the paneling on the "bottom".