parents green card

Hi:



I am US citizen. I am thinking to apply green card for my parents.



I have two questions:



(1) how long does it take to get green card if they are here, and if they 

are not here?



(2) My dad has Parkinson's disease. I wonder if he qualifies for green card.

I checked the physical exam for green card, "Classes of Inadmissibility" 

defines "People likely to become dependent on need-based government 

assistance". He needs my mom to take care of him everyday. 



Anyone has experience?