Hey Kevin H,
Futozao shamisen that are in the Tsugaru style are the most expensive shamisen by nature. For one, the size of the neck is thicker, and it uses more wood.
Other differences are in the skin used. Hosozao shamisen (used for Nagauta, Kouta etc) uses the belly of the dog or cat, which is the thinnest and most fragile part which will produce the proper sound for the genre. Tsugaru uses the backside of the dog, where the skin is thicker. As we all know, Tsugaru requires a very rapid and heavy bachi syle, and the skin has to be thicker to withstand the beating that goes along with the style.
Nagauta with real dog skin are normally around 700 dollars new. Tsugaru with real dog skin are generally around 1,000 dollars new. Anything below 1,000 and you are either buying a used shami (which can be a great deal!), or you are looking at a shamisen with synthetic skin.
Do not worry too much about buying a beginner level Tsugaru shamisen for now. You can get by with a nagauta shamisen for Tsugaru, using the correct koma and bachi. You just have to be a little bit gentler on the Nagauta shamisen to be careful you do not break the skin.
I would say you should wait until you are ready to upgrade to around a level 3 or higher shamisen rather than investing in a Level 1 with fake skins, because chances are: your nagauta shamisen makes a better sound.
The Level 1 Tsugaru Shami doesn’t have Sawari installed, but Level 2 does. Its not an absolutely necessary option, but its found on higher level shamisen for Folk Songs, Tsugaru, and like Keven K. said: sometimes Jiuta.
Seriously though, just wait until you can afford a level 3 or above. Anything below would be a waste of money since you already have a shamisen that can teach you the basics of playing. When you become more advanced, and feel up to making the investment, then you should definitely upgrade to a Tsugaru shamisen. Until then, happy practicing! 