Do what my brother does- ride it til it’s falling apart, then stick it in the cupboard under the stairs for 3 months, then bring it over to mine and say “It’s not working right, not sure why”, and watch as the old chain has to be cut off with an anglegrinder as it’s corroded into a single lump. Then complain that £30 for a new chain, mech, cable and cassette is a bit expensive.
Oh aye, me. Squirt wax, then sprayed over with ACF50. Squirt isn’t up to it by itself, can be sticky and doesn’t seem to prevent rust at all. ACF50’s a nonsticky corrosion inhibitor I’ve used a lot on the motorbike, and it seems to protect the Squirt and also keep the chain rust free and reasonably grime free. Might be better options but this works well enough that I’ve never bothered.