If you get students who call, and you're okay with students, what I did was say that students may have someone else paying their rent, but I still did not want a co-signer on the contract. 

Uncollected rent is probably gone.Get possession, CYA, get it re-rented and consider tweaking your lease agreement terms as well as asking for a co-guarantor, where possible, in future.

And I almost always get a co-signer on the leases. 

I promise I'll pay, and put it in writing, but not in writing as a co-signer? 

The co-signer must also be COLLECTIBLE and have the same qualification to qualify as the applicant who plans to be the tenant.POSSESSION OF THE HOUSEEvery person who will be in Possession of the home, that is of legal age, must be on the lease and must qualify, therefore be COLLECTIBLE, or have a Co-signer.AND ALL OCCUPANTSWhen you type up a lease you should always have on all legal forms the tenants names and these words "AND ALL OCCUPANTS.

I completely agree with @Daniel MohnkernLook at:Length in Field of EmploymentRent to Income RatioCredit ScorePayment HistoryCriminal historyIf they screen well on these ccategories, you should be just fine.If things look iffy, get a double deposit or a co-signer.

Although, I have a co-worker (and landlord) that is from NY that says smooth is what he is used to....guess it is a regional thing.

It specifically states a CO detector must be within 15' of each bedroom.

I got turned down by several landlords who wouldn't sign a lease without a co-signer until I found a great landlord who took the time to understand my situation.

First of all, if the father is not on the lease, including as a co-signer, then you shouldn't be talking with the father at all.