The Professional option would be Adobe Illustrator coupled with a drawing tablet. But with illustrator costing in excess of £500 and a decent drawing tablet in the hundreds too, it all depends how serious you are about wanting to do this. There are freeware options out there but I know nothing about them.
You would also need to factor in a printer capable of printing onto heavyweight papers (assuming you're cards aren't made from 100gsm copy paper?).
Thanks for your response. The Fonts on Microsoft Office have been fine up until now. I have not used any professional software for illustrations before. My budget is between £300-£500 to spend perhaps 2 different types of software. Does that sound reasonable in your experience?
My other half is in the process of setting up a business producing bespoke event stationery so I know where you're starting from. Luckily she's got 5+ years graphic design experience and software knowledge so it's one less hurdle to jump.
• CS6 is the most recent illustrator. I use it at home and it's by far my favorite edition so far (I've been using it since CS1). The illustrator basics are quite easy to learn and Adobe's Lynda tutorials are certainly something worse looking at! I believe CS6 is now the only version Adobe sell (older editions are available second hand but you'd need to know the serial nº hasn't been used to upgrade as it won't be valid anymore).
• I use a Wacom Bamboo and it's a great entry level tablet but I'd recommend researching the alternatives as the market is pretty huge.
• We've just bought an Epson printer (cant remember the model number) which seems to handle thicker papers pretty well but the print onto thicker paper looks a little bit grainy. I can see it being replaced within 12 months. Using local/trusted print firms is likely to be your only option for some things but will mean your unit price will increase. It's also worth making friends with someone who owns a hot foil press for the really special jobs which include golds, sliver etc..
If you have the funds and the ambition to learn Illustrator, then that is a great choice. The Wacom Bamboo I would also count as essential, as even if you're not using it to draw, its still a really great bit of kit to have for manipulating and colouring illustrations. Printing wise, you can do it yourself, but for the paper and the printer you would need for top of the range professional results (as a lot of brides to be expect!) you'd probably be better using your local printers, at least for the beginning.
If you're taking it seriously, definitely go for Adobe Illustrator. You don't 'need' a tablet, but if you want to buy one also, they aren't that expensive anyway.
I learned to draw with the pencil tool in Adobe Illustrator using a mouse and can create detailed vector illustrations with a mouse, I got so used to it, now when I try to get used to a tablet I cannot at all, and keep giving in. The tablet makes my hand cramp and it's a massive learning curve trying to control it, as it's become so comfortable with the mouse.