What are some low cost internet service for seniors?

The local library usually has that for free.

You'd probably have to call the various internet carriers to see what is available. I assume your Dad still uses a computer on a regular basis?

Why I asked is because my Dad use to be on the computer all the time, he even coded new programs to use, etc. but in his last year, he didn't even go on to check his email mainly because he couldn't remember his passwords, even though he had them written down "somewhere". I would get Dad new passwords for his emails, etc. and those got lost or he went over his limit on typing in the password and would need to create a new password. Eventually he just gave up.