If you tend to get Guitar Acquisition Syndrome (G.A.S.), you'll save a ton of coin by learning to play orthodox, as opposed to southpaw. Manufacturers certainly don't offer the selection of southpaws as they do in orthodox, and they're typically more expensive as others have already said.
An orthodox guitar can be converted to southpaw, but this should only be done by a qualified technician. There are primarily two considerations:
1) The Nut
This will need to be replaced, as filing slots for the larger strings will leave you with wide / deep slots for your smaller strings. This will create a buzzing nightmare with the string action. Also, simply turning the nut end-for-end is unlikely to work, as they are typically shaped for the installation. A TUSQ nut (by Graph Tech) can be bought for about $10, but should still be swapped out by someone with the skill and tools to do it right.
2) The Bridge / Saddle
Unfortunately the saddle cannot simply be turned around. The saddle is at an angle to the strings which is necessary for proper intonation (uniform note pitch up and down the neck). The saddle slot in the bridge of an acoustic can be filled and recut at the opposite angle, but replacement is the best way for a solid job. Again, a TUSQ saddle can be had for about $10, but the bridge assembly will vary a lot depending on the type of guitar (electric or acoustic) that you have. The saddle slot on a classical guitar is pretty well parallel to the strings, as the shorter fretboard (17.5") doesn't require the angle of the others which have longer fret boards (18" or more).
I hope this is somewhat helpful.
