Formless, nice advice but very to the the book. There are other reasons.
My advice is that you first do orthodox to get yourself comfortable with your 'style'. Then after you know you have a good command in both offense and defense, try and learn Southpaw.
The reason you learn to fight in Southpaw if you're naturally an Orthodox is not because of the stupid reason "If you get hurt on one side and you need to switch" which isn't going to happen. No no. The reason you fight in a Southpaw to begin with is when you're matched with an opponent who has better skill or more experience. There's no way you could in a short period of time catch up with him, hence you use your 'dominant' side to lead with (if you're right handed, southpaw, if you're left-handed, orthodox). Not only will you confuse him, you're making it easier to hit his vulnerable spots by opening your own. If he's naturally a right-handed, but fights in Orthodox, but you're right-handed but fight in Southpaw, you will have an advantage over him because not only are you able to hit his spots easier (remember, he has the same option now) you're hitting them with your dominant hand while he's not even though he has the same option.
For example, you're standing in Southpaw, he's in Orthodox. Both of you have the option of hitting the ribs, which is exposed because of the stances you're standing, but the difference is you're able to hit with your dominant leading hand, while he is only able to hit with his non-dominant hand.
Another reason for doing Southpaw if you're right-handed is simple. It's a heck a lot easier to go on offensive with your dominant side doing the lead. You'll be nuking out blows that'll rattle his ancestors if you were to compared with your left side.
The reason why you don't start training in Southpaw to start with is also something you should figure out. Go, now, and reflect on what I have written. Danny, I know you have an attention span problem, so go think about this and if you have any questions just keep asking. The wise knows he doesn't know and will ask.