Since I got my Anaconda, I have been using that for trade. However, I used a Type-9 to get to the Anaconda (Cobra > T6 > T7 > T9 > Ana). With no shields and properly fitted (read: not all largest class modules), it can run 528 cargo (with a docking computer) and jump over 13LY. On any decent run, that's at least, bare minimum, 6mil an hour. A good run, of course, would net you a little more.
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The sale of that ship is about 90mil, meaning you'd need to earn about 100mil in that ship before you could buy an Anaconda and fit it for trading (which is my preference, because it can run 448 cargo WITH shields and jump a good deal farther, and it handles better). So you're looking at about 15-20 solid hours of trading in a Type-9 to get to an Anaconda if you sell the T9 (of course, this might change in 1.3 with the resale tax on modules). In a Python, you're probably looking at only a little less than double that.
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This is, of course, assuming that an Anaconda is your goal. After all, if you're buying a Type-9, the Anaconda is really the only ship that you could be looking to afford that you cannot already.
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This is also assuming you're playing in Solo or Private Group. If you're playing in Open Play, you need shields, but I'd still say a T9 is worth it if you're looking to make a lot of money.