Re: Would like to convert from 26" to 24", Assistance please
hubs are hubs. you can lace them into any other wheel, as long as they have the same amount of spoke holes as the new rims. a lot of older 24's and low end ones have less spokes. so whatever you're buying, make sure they have the same amount.
if you're changing out wheels, you can upgrade to thicker spokes, too. you might have to drill out the holes on your hubs, but most hubs have enough "meat" on them, and it's common practice.
another thing to think about is to just buy a whole new wheelset. once you buy the rims and spokes and pay someone to lace them up, you might be into it for more than a new set.
Worksman sells a 24" clincher wheelset with 11g spokes, rear coaster brake and a front drum brake hub for around $200. i think they have other hub options, too. (gears, etc...)
and Flightrisk above, has some valid points about cranks and brakes.