I have an eMate 300, paid $40 for it. It's a steal at $20,
if it has the power adapter. Without the adapter, good luck finding one the doesn't outweigh the cost you paid for the eMate itself. You really need the original power adapter for this model, any others can lead to power issues and eventually a fried motherboard. It was used on the Newton 2000/2100 and eMate, 9W.
To connect it to a computer, you will be looking at only two connectors, one is the Newton InterConnect cable, which is an exceptionally rare cable. The most common one that you will find is a DIN-8 connector. This will connect it to the AppleTalk port on the back. You can find this cable usually for very cheap, and it will work on any pre iMac G3 mac. You will need to install on a computer Newton Connection Utility for Mac, which can be found on both the Macintosh Repository and Macintosh Garden. This only works for computer from Mac OS 7 to 9. Otherwise, you can connect to Windows with the appropriate Din8 to DB9 serial cable, which costs all too much right now, (but you could make one). You will also need Newton Connection Utilities for Windows which is also available with a little digging. To connect it to Mac OS X, you will need to have the DIN-8 connector as well as the DIN-8 to USB adapter from KeySpan, which is selling about $30 when it comes up on the market. You will also need as you might know NCX, which I do not have much info on regarding a Tiger version. This is a very good program to use and it can be helpful when using this machine.
Internet on the Newton is possible, and it uses a very specific Wi-Fi card. The WaveLAN card is the only common one that works almost right out of the box and has the most support. You can connect to the internet, but you cannot use it to transfer data from the computer to the eMate.
Loading data on the Newton is very simple if it connects. If it doesn't, check the port configuration if on an older mac or windows. Otherwise, you might have bootstrapped it. Finding .pkg files and programs that you want is very easy, places like unna.org and pda-soft.com will be a godsend. They should work right out of the box, but if they don't they will need to be converted, check the links I provide below.
Other things to look out for if you do buy it or have a pre-purchase inspection; see if the hinges are loose or the display cannot stay up. If it can't then you will need to disassemble the entire unit and fix the hinges and reinforce them, and make sure the display cable didn't puncture. Otherwise you will need a new cable or display. Batteries are a hit or miss, the thing is 20 years old. They might last, but you can always rebuild the battery if you want considering the thing is just rechargeable AA's.
Otherwise, that's all. Sorry for such a long post, but I want to get as much info out to you now so you don't get a dud.
Links:
*Make your own Newton-to-PC cable (ca. 1995)
https://www.nsbasic.com/newton/info/technotes/cable.html
*Newton Connection Utilities Basics Manual:
http://www.newted.org/download/manuals/0307273ANCNCTMOSUM.PDF
*Keyspan DIN-8 to USB:
https://www.ebay.com/itm/Keyspan-Tw...298021?hash=item3f892bf125:g:128AAOSwaPtZ3viF
*Wireless Card:
https://www.ebay.com/itm/APPLE-NEWT...237102?hash=item4ac137c36e:g:BBkAAOSwIgNXoLk0
*Power Adapter:
https://www.ebay.com/itm/NEW-in-box...350471?hash=item4b268d6f47:g:fjsAAOSw-QZZxGiZ
*Newton Software and help:
unna.org ,
http://www.pda-soft.de/english.html ,
http://myapplenewton.blogspot.com
Good Luck and Welcome to Newton!