I got a used bird cage used for a dog kennel (mind that the bar spacing
is not more than and Inch or the fuzzy will get out)bought some pvc
coated chicken wire ($15.00), Cable ties ($6.00), Bird step ladders
($4.00 each), wooden rods ($1.00), some fabric remnents ($7.00), needle
and thread ($2.00).  Because I got 4 ladders and 4 wooden rods it cost
me about $53.00 to make my 5 level cage for one ferret.
 
I measured the chicken wire to what I wanted for the shelves and then
tied them onto the cage using the cable ties (the part that is cut goes
on the outside of the cage as to not be chewed on).  Then I put the
wooden rods across the edges of the wire mesh inside the cage to make it
more sturdy also attached with the cable ties (the part that is cut is
under the level and tucked up into the level).  I cut the wire mesh to
fit the inside of the ladders so the little feet didnt slip through them
also attached with cable ties.  After all that I sewed the level covers
together as giant pockets to sleep in (to avoid potty problems on other
levels).  It took about 2 days to complete.
 
Here is a link to a picture of what mine looks like:
http://i36.photobucket.com/albums/e10/ButterflyKnightja/FerretCage.jpg
 
I have not had any problems of them chewing the cable ties but if someone
knows a better way of attatching the levels I am open for suggestions.
[Posted in FML issue 5182]