Cassette decks....reliability and build quality...

Cassette decks are fairly complex devices. I would stay away from used, older decks due to maintenance issues. Even the best built ones require a good deal of TLC. A decent quality new Tascam or Denon deck will cost around $400. You could get lucky on an older deck, but you could get unlucky just as easily.

In a different direction, any sub-$200 USB A/D attached to a computer with recording software (usually bundled free with the A/D) will allow equal to if not better than cassette quality recordings, plus editing.

The best cassette deck I ever owned was a Nakamichi CR7a. I was able to make high quality tapes, but the phrase "the ultimate in fidelity" never crossed my mind. When compared to the original vinyl the casette always sounded slightly congested and electronic.