>buy <$20 1950s cruiser off marketplace
>get out the wire wheel, sandpaper and grease
>remove all internal rust and repack all the bearings, service the headset, service and true the wheels and coaster hub, etc
>throw some BMX bars and a decent saddle on it that you harvested from some discarded piece of shit that you found in the trash or in a ditch
>leave the the entire exterior of the bike rusty and filthy
>ride it until the wheels fall off
This has been my modus operandi for years when it comes to commuters and knock around bikes. I like old European 3-speeds like Raleighs and Crescents, and 80s American, Italian and Japanese road bikes, and 90s MTBs, too, and have pristine and fully restored examples of all of those in my workshop/shed, but I'm always just reaching for my $10 piece of shit I leave leaned against the wall of my house open to the elements year round. Nobody wants to steal them, they're practically bombproof, and you can just jump off it and ghostride it into the side of a 7-11 with no cares in the world, go in for a slurpee and a microwave burrito, and when you come out it'll just be laying there ready to take you home. It's like being 12 years old all over again.