A couple of things to remember when buying a used spa. You should see the spa running. Check the equipment bay for leaks, and look to see if the spa is up to temp and the pumps and such work and sound good. Check the cover, cabinet shell etc.
Consider what it will cost you to move the spa, install and wire.Call the local dealer for that brand to see if they will service that spa prior to you purchasing it, they may even have a service history for that unit if it was purchased there. Check on the cost for a service call. There is usually no warranty available to a second time buyer.
On a side note, although Caldera and Hot Springs are owned by the same Parent company, I would not put Caldera on the same quality level as Hot Springs. If you purchase a Caldera, my advice would be to check over the shell carefully.