Even though I started playing on one of those glorious sounding 12's (well, I played a 6-string for half a year before), I would not recommend starting on a 12 unless you only want to go for campfire cowboy-chord stuff. Picking and other advanced techniques are painfully difficult on a 12 - even though they are fun, once you master them
Should you go for a 12, please do not try on anything less than a Yamaha FG720/12, a Tanglewood TW145/12 or the likes.
And have it _-*professionally*-_ set up by a luthier for the strings of your liking, e.g. D'Addario EXP-11's.
Even then, prepare for some serious pain in your fingertips.
I know, a 12 is the King of jangle and there is nothing that even comes close to full chords on a 12, but - get started with a 6-stringer first. You can always add a 12 later.
You know, you're not supposed to have more than one partner at any given time, but there is no law that restricts you to only one guitar. Best thing is, that in contrast to partners, guitars don't get jealous. So I currently have three 12's and 7 6's... and I love them all.
I'm going to echo Karsten Topp both on the choice of guitar and getting it setup. I started with very low end 12 string and if you desire to set the frustration level real high go cheap. You will find that when playing a real low end 12 string the guitar will sound in tune on one portion of the neck and sound terrible when you move up 5 or 6 six frets. Leave that misery to someone else.
The Yamaha 12 has great sound and playability for the money. That's nice combo. I currently do not have a 12 string but I have made the mistake of buying a cheapy - (I think I bought it at Montgomery Wards around 1967- they did not offer to set the guitar up). About 3 years later I bought a Guild 12 that just had a beautiful bass sound and followed that up with a Gibson B45 12. Beautiful mid range sound but alot of $ at the time.
I sold the Gibson to help get a down payment on a house. God I regret that. Hmm - I really should let that go.... Sorry I digressed....
Better to add this later than never for future users. I don't recommend a 12 string for beginners period. Whatever guitar you get you are going to need to have it set up professionaly. Most guitars in the under 800 dollar catagory are going to frustrate you and you will become dicouraged rather than enjoy the extra posiblities in tone provided by a 12 string.
During my own extensive search in Southern California area I found only two 12 strings Guitar models come to mind here in the under 700 dollar arena. The Breedlove 250 size 12 string guitars sound nice and are easy to hold on to (vs. a jumbo )and play very well. Last but not the bit least I was happily surprised by the The Martin DX12. It goes for around 599 probably less with a little haggle. The DX12 sounds great and was very playable right off of the shelf. Myself I opted for saving a little extra cash and purchased the Breedlove Jumbo 350 maple 12 string and had it set up proffesionally. Enjoy.
I would also recommend staying clear of inexpensive 12 strings, especially if you are a beginner.
I owned several inexpensive 12-strings including Takamine and Ibanez models. For several years my only guitar was a 12 string. I loved the sound, it was difficult to play, but the really frustrating part was that it was only in tune on the lower frets, so it really limited what I could play. I have been playing fingerstyle on a 6 string for a few years now and my playing has improved greatly. I would try a 12 again but only if it a good one and never as my only guitar.
Here is a quick way to tell if a 12-string is worth your trouble:
Tune the guitar. Make a harmonic on the 12th fret and then finger the 12th fret, repeat several times. Do that for each pair of strings. The fretted note pairs should match the harmonic note pairs closely and be in good harmony with each other. If not, any notes on the higher frets will sound "off" no matter what you do, put it back on the shelf.
Just for kicks check out Luna guitars. I purchased the Trinity 12 string from Overstock.com. This company uses Dean to help market their guitars. The guitar looks great and sounds great without plugging it in. The quality was very good, no excess glue, pit in the finish, no gaps in the joints and the frets were finished correctly. Not bad for a sub $300 12 string. It required little set up and the intonation was right on. It has a built in. Tuner and a 3 band tone or equalization built in. Plug it in and it sounds outstanding. Just my $0.02.
In Reply to Dave Cowgill response- Regarding your Just my $0.02 comment. Some time you get what you pay for. The modern manufacturing processes applied to these guitars Lunas, Rogue's,etc. Make most of them playable out of the box without many intonation issues or with a professional Setup even better. I know I recieved a "free 6 string" with a box of strings. I did a setup and it plays better than many of my friends more expensive guitars unfortunately the tone is not so great but it is fun at the beach. Construstion processes where used that increased profit and not quality. Corners were cut in materials cost. All of which effect quality and tone of this instrument
Now why did I bring all this up you ask! This was a newbie requesting a beginning guitar. Right?
Myself (not a teacher) and most insrtuctors I have met don't think a newbie should start with a 12 string. It is a recipe for someone to just give up, it is hard enough to learn a 6 string in the beginning.
My other reason for mentioning those guitars is I have tried alot of guitars in the lower price point area and although some of them impressed me with there playabilty thay all sounded like CRAP!
I got bit by the 12 string bug because of the the way they sound. A good luthier can take care of most playability issue. But he can't turn Pine plywood into Rosewood.