A very interesting idea. However I would suggest you look at either online sites or local printers to actually print your designs. I imagine you would have a difficult time trying to come close to the quality from professional printers. The prices might be much better than you think. Upon a quick check on the web I found these sites for possible solutions. If you search you can probably find better ones.
http://www.customplayingcards.com/index.htm
http://www.tmplayingcards.com/playingcards_basic.php
http://www.tmcards.com/
I figure if I am going to do stuff like this whether it is brochures, business cards, or like what you want, custom playing cards, it is usually worth doing it right so they last a long time and look better. If I were to print them myself I might consider a very smooth and stiff cardstock, then fill the entire page with as many cards as I can, then printing the other side being careful to match the cards up (not easy) and then getting the sheets laminated or UV coated somewhere before I cut them down. To cut them you might be able to devise a template to cut around. A lot of work but it might work well enough. Good luck and please let us know how it goes.
T