+1 but be forewarned, you are not going to get rich doing this since the price point is pretty low for cards (plus the fact that people are not using the mail system as much anymore.
Check prices on Etsy for some current thinking on what to charge. Hand made cards go for anything from $2-5 each, or maybe 8 cards for $12-20. A lot depends on how artsy they appear to be. I did all the math on a spreadsheet last fall, trying to figure out if it was worth trying to sell cards at a local artisan show held on my campus. Short answer: No. Longer answer: I would have to spend a lot of money on materials to get the per-item cost down to a reasonable level, meaning I would have to sell a LOT of cards to make any sort of decent money. Hundreds of cards, at minimum. The printing and packaging time would have been prohibitive.
You'll likely want individual plastic sleeves for each card, or small clear plastic boxes for sets. Clearbags.com supplies these. Don't forget to factor the shipping costs into the per-unit cost of the materials - I was surprised to see how much that mattered, and it has an impact on how large an order becomes cost effective. (Larger order = lower per-unit shipping costs.)
That said, I do like the Polar Matte cards from Red River. We use them for holiday cards, and small gifts, and I print personal work to send them as thank-you notes, etc. It's cool to see the cards displayed on people's desks or hanging on their bulletin boards.
