Deaf in one ear - moderate hearing loss in other. Must I buy two aids?

If would help everyone if you could post your audiogram for both ears, this would enable us to offer advice, two is always better then one, as for BC I’m unsure what your question is about.

A Cochlear Implant assessment may be helpful for you.

The other thing you could do is investigate BICROS type of hearing aids where the aid in your deaf ear sends sound to your better ear, making it much easier to talk to people on your deaf side.

I am deaf in one ear and significant loss in the other. I have declined bicross my entire life. At first it was because back then it was wired and that was a non-starter for an active kid. When it finally became wireless, I declined for costs reasons and for the simple fact that it won’t return stereo hearing or sound locating ability. So for me the extra $$$$ for some more mics wasn’t worth it.