Husband and Wife both fill out rental app???

[Ian W.]

Renting an apartment building and wondering if both wife and husband should fill out an application? Is it standard to have all people 18+ in the household fill one out? 

In this particular situation the wife filled out an application and her credit score was pretty bad (531) and supposedly he is over 600; how much do you take a situation like that into account? They both have good income.

How invasive can I get with questions; thinking of asking for two month's bank statements to prove income?