I started with 70m. It helps to stick around and watch your offers (I have two monitors, so I usually do work on one and have RS open on the other), because then you can flip large quantities of more expensive items without having the cash to put in the big offers. Now that I'm at 180m (and classes have started), I've fallen into more of an inactive flipping role, mostly putting in offers for 20m - 40m items with low trade volumes but 1m+ margins and I just clean them up when I get the chance.