I started doing the same thing just after the RAF system was released.

Your referred account, once you pay the $20 for WoW Classic, gets 30 days of account time. You'll be limited to level 60, and will not be able to play BElfs or Draenei unless you also purchase Burning Crusade. If you are uncertain that you want to commit to dual boxing, you might want to only purchase WoW Classic. You can always buy BC when you're @ lvl 60.

The tripple experience is incredible. On later quests, I was getting 20,000 - 30,000 XP for single quest turn ins. Every few quest turn ins was a Ding. Summoning your linked toons is also a great way to speed things up. I would send a high level toon on my main account to a new location, and then summon a RAF toon to pick up a new flight point. Then the RAF toon would summon his leveling buddy from the main account there to pick it up. It's limited to 1 summon per hour, each direction.

The gifted levels must go from the RAF Account to your Main Account. You can only gift levels to a LOWER level toon. You cannot gift to someone past level 60. For the most bang for your buck, you could gift 30 levels to a level 30 Main after your RAF toon hits 60. You would basically end up with 3 new level 60 toons doing this (the gifted toon and the 2 you tripple XP level up to 60).

You'll need to fund the 2nd account with 2 months if you want to receive the Zhevra mount on your main account.