I am using a Chinese ZJ-5890 thermal receipt printer that can be bought on ebay for about 25$. It uses standard 58mm receipt rolls that can be bought in any office supply store. So the cost of running is is very small. I would however suggest that you do not use this to follow twitter accounts with a few 100 messages a day, or you will have a lot of paper on your desk.
It needs a computer running linux (of course) and Python. These days you would probably use a Raspberry Pi Zero W, but this project was built back in 2017 and I had an old ACME Systems Arietta G25 single board computer laying around so I just used that.
As hardware modifications go... I added a small buck converter board (2$ on ebay) so I can use the printers internal power supply to run the board as well. Plus I glued on a few magnets and added two pieces of wood to hide all of the electronics inside the printer itself. But all of those modifications are completely optional. All you need really is a POS printer and a computer running linux. Plus the software scripts that I have written.
For more details please go to the github page and see what is there:
If you have any questions... please don't hesitate to ask.
One of the coolest tricks I've seen with Raspberry Pi and thermal printer is a "selfie printer" that @eliot built and brought to #2018 Hackaday Superconference -- it used a Pi camera and converted your face to ASCII art. Very cool.
I couldn't find a link, but here's a talk he gave about fun with Thermal printers https://www.youtube.com/watch?v=SwjkHvF0GFM
I like the tweet printing, just mentioning this if you're looking for further enjoyment.