See "Bling" for more info.
An achievement that does take quite a bit of preparation, but is very possible. When starting Build a Label, instead of buying anything with the money you start with, invest all of the money you earn into Luda's song. With the money you earn from it, invest everything you have into your second song in order of importance. Do whatever you have to do save up until you hit 3 million dollars, so don't go shopping for clothes or jewelery, and try not to give your artists too much with royalties, around 30-35% is fine. Once you save up that much, whenever you get a new song to invest in to, max out every possible stat. With everything maxed, go do three or four fights. After that time, your song should have gone multiplatinum.
When it comes to the song you want to release, make sure you do not release any other songs at the same time. Releasing multiple songs takes away money you could use to invest into one song, and they both will compete for sales, usually getting beaten out by competitors in the end. It's always better to focus on one song, as it will easily make the sales if you invest everything you possibly can.
Also, it doesn't matter what your artist's approval rating is when you release a song. Approval only affects how quickly an artist will make a song, so you don't have to give into their every want. Of course, keep their approval up, but you don't need to give money whenever they ask you to. It's also highly recommended not to get any girlfriends if you are going for this, as they require a lot of money to keep happy. Since you really have to save up, it's nearly impossible to get both this and "Ladies Man". So before you start your playthrough of Build a Label, plan on which one you want to go for.
Make sure you release the song you want for this achievement before Luda asks to go out to the club, or else you won't have enough time in the game to get the sales you need.
You must sell 2 million units for this achievement.