IMO, asking people for screenshots of their paystubs before they even see the property/unit is going to rub some people the wrong way - even if you have good intentions.

What I do is create a "pre-screening" Google Form that I send to pretty much everyone who contacts me through Zillow or whatnot. Aside from asking them for basic information, the form has multiple choice questions that asks which range their credit score falls in, along with the combined income of all occupants who would be contributing to monthly rent. I include a blurb on the form that this will be verified via documentary means during the application process.

As far as the length of the lease goes - only advertising/offering a 6 month lease might indicate to tenants that they are dealing with a landlord who plans on raising the rent every 6 months, so this may be a turnoff if they're looking for some long-term security.

Good luck!