As well, being on a budget, means the work bike needs to be solid as f**k, because if you bust it you have nothing to work on to make more money. Being a messenger is hard enough, without not having a bike to ride. Save up and replace stuff with nicer gear as it breaks/wears. Those nicer components/frames ... save 'em for the 'after work/weekend bike'. Once you have several bikes then you can afford to risk wasting something it took you a year to put together. Same reason I won't commute on my CF road bike, despite not having crashed in over ten years on the streets. Good wheels though will save you time/money/grief.