If I understood correctly , you let people design bussines cards and then you print them and send them. The idea sounds awful. Everybody can create an "bussines card" even in paint ,put them on a USB drive an print them. Try buying an 3D printer and give people something else 
I am not talking only about business cards, we can print and cut everything that goes on paper, stickers, T-shirts, etc.. (later we will add everything you can imagine,from figher lighters to pens, stamps, and so on).
And when app will be ready it will be free to use to make whatever you want and if you decide so you can print it or not.
Yes everyone can print what they need, but it's not same quality
About 3D printing, we are thinking that way but let's start with something that's already running nicely in our country.
I wish you best of luck. I think there are many other like this in your country (as in mine), so doing this online I dont think that you will succeed. Maybe an offline shop it will be better. A bussines man/company wont have time to design his own card/sticker/stamp/etc.