How do you put a stage to perform plays in your backyard, without spending a lot of money?

Hmm... well, let's see... theatre is all about illusion... making things seem much more elaborate than they really are... so... the easiest thing to do would be... instead of building a stage that is set off the ground, put up a cyclorama or a scrim... they are stretches of canvas that seem to make a solid wall in the background... these are easy to create the illusion of a stage... you can add scenery in front of them, and even paint them, if you have scenes in one spot... a great way to make the illusion of a stage would be to create a proscenium... it's basically the sides and top of the front of the stage, usually where curtains are... it sort of creates a picture frame for the stage itself...