relocating applicants, cosigners and additional tenants

[Holly Kent-Payne]

I own a duplex and rent out the first floor. After renting to a friend for the first year, I am now in the process of screening tenants. I had my criteria written up before accepting applications, but of course some strange situations have come up that I didn't expect. 

*relocating adult couple with local co-signer (I was expecting this situation more for young people with little credit history). The co-signer is a friend, not a relation, with 200k plus income who will be employing one applicant as a personal assistant. Other applicant is disabled and the first is his caregiver.

*relocating applicant with two children who wants to be able to add the fiancé/father to lease in several months (after he's released with charges dismissed.) Also has a cosigner who's a relative. 

I am not looking to rent to either of these applicants since I have other options and there's a fair few red flags flying with both, but it's made me realize I need to add a couple of things to my criteria for the future. I'd like to better prevent these kind of 'messy' (for want of better word) applications! I know owner-occupiers have a bit more discretion for selecting applicants but I will be moving out and renting both units at some point, so want to be prepared with solid criteria. Looking for advice from anyone who addresses the following in their screening criteria:

*out of state applicants applying sight unseen. I want to be open to people relocating because I've had to do it myself and know how hard it is, but at the same time it is a bigger risk for me to take on. Does anyone not allow these applications at all, or allow only non-cosigned applications? 

*co-signers. I know I am not obligated to consider applications with cosigners, but if I do can I specify that they must be a relative or allow them only for certain situations (ie. younger applicants). Have you ever had a situation where a cosigner is also the main source of income through employment?! What about sight unseen applicants with co-signers? And do you weigh cosigned applications equally with those who meet the requirements on their own?

*adding additional tenants. I'm not comfortable with renting to someone who states they will want to add an unknown person who I can't currently screen to the lease later on. It seems like a big risk of having an unapproved person move in anyway, or the original tenant breaking the lease if the other applicant is rejected. Am I within my rights to reject an application on this basis alone?

Thanks in advance for any insight you can provide as I am new to this process.