Visit visa docs for in-laws holding Canadian PR

Hi All,

Wondering what docs would I need to provide for showing "strong ties" to home country for my inlaws visiting us for 10-15 days max. All of them (father, mother, sister) in laws are Canadian PR holders with Indian passport.
1 - Father in law's bank statement, house papers (India). (retired with no pension so no money incoming apart from his son sending from Canada and shop's rent incoming)
2 - How much money per person to show is recommended?

They do not hold any assets in Canada other than their son and daughter homes and their jobs.

Any other things I need to be wary of?
Thank you