I started with the D5000 which is a great (or great-great) grandparent of the D5500 and moved on to the D7100. Both are very good cameras and I'm sure the 5500 is too. That said, if you're already using a non-compatible brand, switching to Nikon (or Canon etc.) for a "backup" doesn't make sense to me because then you're in it for a whole stable of lenses just for your backup. That'll run you into $$$.
Just curious what price you are talking about?
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