boy friend and girl friend with small daughter want to rent my h

I am wodnering whether you share your comments to How the landlord should treat co-signer? should we require each co-signer qualify the whole rent or just portion of the rent?

I just received one application to my house. they are boy friend and girl friend relation with small daughter (not sure if this daughter belongs to any one of them or their generic daughter). the man has 3X income (3K month income while the rent is 1K), the woman will quit her current job and will find a new job locally. so I can not count her salary.

Man credit score is 670 (quite good)  while the woman may only have 550. I am little bit worry about that. Since they are not legally bounded marriage, if they broke up,  the man can just walk away while leaving the woman has no way to pay the rent.

how to deal with this situations?

 

thanks