Do most apartments use third parties to screen applicants?

To further clarify, the investment property will be purchased with100% cash that was obtained from the HELOC so there would be no loan applications at the time of initial purchase.  

But even that site has caveats, is clearly sampling only SFRs (not reasonable in high density metro areas) and assumes a $1,000 rent which not even a national average nor applicable in many cities.If only this kind of analysis could be automated and kept up to date and be more inclusive.

I’m thinking I should have the two brother fill out applications and if they pass have all three sign new lease and not extend time.

Just keep reading, listen to the podcasts if you haven't started already(SO motivating and filled with a wealth of applicable information) thanks @Joshua Dorkin and @Brandon Turner.

I suspect that this will give me more applications so I can select the best tenants.

But with the hard money lenders, they're just going to ask you to submit a loan application and an itemized list of the repairs.

Do you have a formal application and screening process developed?

I got it off HUD auction and it has too many use restrictions for any lender to lend on it; and buyer's loan application is getting rejected from many places.

Also Application fees?