BeccaB, Unlike alpine boots that work with any bindings your boots must match with you binding. If your boots are NNN then your bindings must be NNN. A NNN Back country boot will not work with NNN bindings meant for classic skis. Salomon SNS boots will not work with NNN bindings. Also some skis have tracks that are already mounted to the skis and only certain bindings will fit on them. I didn't study skate ski boots and bindings.

Then you have to find a boot that fits well!

Unless you know what boots and bindings work together it's better to buy from a store such as REI or the numerous online nordic stores.

The boots that fit me well required an NNN binding. I bought my original skis flat (no binding) so I had options with my boots meaning whatever boots I bought the binding were matched to them. My new skis came with the binding and I made sure they were NNN so I could use my old boots.

I hope this makes sense, it was all very confusing to me and I spent a lot of time searching on the internet trying to sort all of this out.

You could buy you boots from a retailer, my boots have the type of binding marked on the bottom and then get your skis from Craiglist. Be sure to do research on the skis and bindings and make sure the skis are appropriate for you weight and intended use.

Also, find out how many times used skis have been used. With use all skis lose their camber, or flex. My downhill skis with 200 days of skiing don't ski the same as a new ski of the same model. I don't know how much use a nordic ski will take but I'm sure they have some type of life span.