1) Learning to play on-line: its great. If you're not a full member for this site yet, definitely sign up. The only draw back is that you don't have someone there to correct you if you're making mistakes or developing bad habits, so that just means you have to pay extra attention in the video lessons to make sure you're playing correctly. Other than that, on-line is far cheaper, you can watch the same lesson over & over again (no more going home saying "what was that the teacher said about tempo??") and you can choose from lots of different instructors, lessons, and styles.
2) What kind of guitar to buy. Well, what kind of guitar do you like to play? If you like acoustic, that's a good place to start, even if you are going to move on to electric later. If you can buy from a shop so that you can try the guitar out, I'd definitely recommend that over buying on-line. Don't go too crazy with a pricey guitar to start with. While there is some truth in "you get what you pay for" with guitars, keep in mind that some guitars have fancy inlays on the fret and decorative work on the body that makes them expensive but does nothing for the sound.
Good luck!