How could Anakin / Shmi afford the build your own C-3PO installments?
Since we see the TC-14 model on da Trade Federation ship, I'm working on the assumption that tiny, little Anakin did not build a droid that looks almost identical by some incredible chance.
My thoughts are that the C-3PO must have been an earlier and now largely worthless design and that it was now available via one of these magazines you see down the newsagents, in this case "Build Your Own C-3PO". For just 1,000 weekly installments, first edition 1.99 credits (then in very small writing, each subsequent edition 9.99 credits) you too can own your very own C-3PO.
It's great that Anakin / Shmi managed to keep up with the payments but I thought they were very poor slaves? Did Shmi have to do something very bad so the boy could get his weekly C-3PO pieces?