you can improve your original audio by looking at the mics polar pattern and choosing one that is very narrow and focussed.

some recording software allows you to fiddle with thresholds and floors which can be quite handy for livestreams.

but for podcasts and voice overs you probably want to fix it in post. most software (even the free Audacity) allows for generation of a noise profile from a few seconds of silence. then you filter that pattern out of your whole audio and *bang* crystal clear audio without fans.