I think that Houdini for hobby its a big adventure... Houdini its getting place to be one of the best effects software now with fluid and particles better then Maya now.
If you want a hobby I think that Blender that its really frre is the better way to go... BUT theres a lot of others softwares like TrueSpace that now its free too... well the list never ends. Try all and use what you think is better for your workflow...

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