I don't know about free...but way way cheaper than buying a 300 dollar cage online.
The paint was the most expensive part. $7 a quart for the latex and $10 for the clear gloss. It should have only taken one can of each but I spilled the latex all over the garage when I opened it..so I had to buy a second can.
Now that I'm sure I like the paints I picked I'll be buying big gallon cans when I go to build all my other enclosures.
Other than the paint, $2.50 each hinges and locks, the furring strips were like $1 each for 8ft.. I used maybe $6 worth, I had planned to build another mouse rack with them but *shrug*
So $45 dollars. Not bad at all. well and 3 days of work... and a $60 power drill, and a skill saw blade, and ect ect ect lol
Yeah if you have a smaller piece of glass or can cut your own plexi it would be very easy to modify down. I plan on dismantling a 20gal tank for enough glass to make 4 cornsnake/bp sized cages. I've got a really junky 20gal from craigslist that the sealant is basically falling off of so it shouldn't be too hard to clean up.
I plan on putting the mesh strips on either side of the door for the smaller cages so there's more floor less height... I just had to put it above the door on this one cause plywood is only 4ft wide and so was my glass.