Item 1: a bathroom
Item 2: darkness.
Replace the bath by darkness, and you will have a darkroom.
On top of what they others mentioned, I would add: get a decent enlarging lens already. You can find a Schneider, Nikon, or Rodenstock for less than 100 USD. Actually, I think there must be some for sale in the APUG classifieds. This is an investment that will last forever, and will give you great results, regardless of the enlarger you pick.
As you will be tearing down the bathroom often, I'd recommend you get a good bubble lever to check your enlarger's alignment quickly. Yes, it's not as precise as other methods, but it helps.