Sponsor parents from uk

hi,

I am a british citizen and own my own 5 bedroom house, my salary is 22k. my parents are both retired aged 60 plus, they visited uk numerous times before 2010,(they had 5 year visit visa )

now they want to come and visit me and my family , i am ideally looking at 2 or 5 year visa for them,
just need to know the documents which need to be attached with the application.

i would appreciate your help on this matter

regards

What is connection to Tier 1?