I don't know... You could buy a new bike (or a really nice used one) with a 3-speed IGH for around the price it would cost to buy and build both wheels and convert a cheap beater into an IGH bike...

It would be a lot less of a headache and work smoothly right out of the box...But if you have your heart set on the conversion then go for it.

I own an IGH bike that has a SA 3-speed. It's almost maintenance free. Woot!

I'm looking forward to riding it in the winter because last winter with my derailleur bike, the drivetrain cleaning ritual sucked! Nothing like having to clean off salt, sand and melting snow almost daily from your cassette and derailleur. Ugh.