I think BellaBoo's advise is good. Shop with your Grandmother and listen to her advise. I have a Janome that is about 10 years old and have not had any issues with it and it isn't fussy about thread and anything else. It is a workhorse and doesn't make me baby it. I love her and would get another if necessary. Also, be careful if you buy a second hand machine since the warranty usually isn't any good with a new owner. Good luck with your hunt.
Sue