Since this is the most time consuming achievement in the game, shaving off a few seconds and adding a couple bucks will do really well in the long run.
NOTE: You must be a decent and consistent drummer with a drumset that has a good snare (red) pad. If not, the other solutions will help you more than I will.
First off, your Gamertag must be signed in on your drumset. Then plug in a mic (wireless mics DO NOT work in this game) and turn on a controller for second player, it doesn't need to be signed in.
Next, go into band quickplay and pick the song "On The Road Again (Live)" and go on expert drums and beginner vocals. Put your mic up to a fan or a speaker so the vocals do not fail you out. After playing the song, make your judgment on if you can consistently FC (Full Combo) this song.
If you can consistently FC this song, then keep playing it, you can make $1365 every 2:28 (Not including loading times).
If you can't consistently FC this song, then read another guide, they will help you more than this guide will.
Some tips before you start:
-Practice the tricky kicks in the song and the ending. Those 2 aspects of this song may throw you off and will make you lose out on some decent cash.
-NEVER activate star power, not only will it be tricky with these rolls, but you actually get more money if you don't activate at all, a whole 10 bucks!
-Take a break every 30 minutes, you have worked hard and need to clear your mind from this very repetitive song. Go make a sandwich or go out for a walk, it will make this achievement much less irritating.
WARNING: This method of getting this achievement may wear down your snare drum pad. If you have an obsolete drumset, (for argument's sake let's say a Rock Band 1 kit) I would recommend using it for this method. Hitting one pad this many times causes a bubble to form in the middle of the drum pad causing sensitivity, how hard you must hit, and overhitting issues.