My 2c worth:
Training on your lonesome is helpful, but training with others is necessary to fully develop.
For solo training, there's probably no need to splash out on a sword (or most simulators). Depending on what you want to do, a weighted stick may be an adequate simulator to get used to the basic positions and movements, although once you have a training partner and need to feel though the blade, better simulators really, really help.
Much more helpful would be a big mirror, or better yet a video camera, so you (and potentially others, even perhaps a long distance teacher) can see what you're actually doing.
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