I have set up several 401ks in the past. The best match I got was not really that great 6% of my pay matched dollar for dollar. I think up front 401ks look like a good option, but for mustachians planning on RE they aren't that great. The most obvious problem is many of us will be retiring far before 59.5 years so we will get hit with a 10% penalty on everything which will really cut into profits. The second issue is the hassle with portability and drawing money out quickly. The third issue is government tampering which is bound to happen sooner rather than later, who knows what rules they are going to change, if tax benefits will remain, will penalties be increased, will contribution limits be changed etc. Another negative is the high fees and the lousy selection of funds. Sure you can make money on it if done right, but due to uncertainty, the withdrawal penalty, and lost opportunity cost, you are essentially working backwards. I am guaranteed to take my money out within the next several years, so even though a 401k is an option for me, I will not be using it.