If you want me to give you a quote, I'd need to know the address, 1st lien details (type of loan, balance, interest rate), credit score, income/DTI details, and target LTV (can go up to 80% CLTV on the 4plex). 

First of all I put my acceptance criteria clearly in the ad: minimum credit score (enter X amount, 620 is what I use),income 2-3x rent, good rental history, references, no evictions, acceptance dependent upon background check and employment verification, pet policy, desired lease term, etc. so that people will hopefully read that and not come to the open house if they know they won’t qualify.

No eviction protection so since you gave to settle on someone with and low 600s credit score if you have to go to court they get to charge for their time on that. 

Your company is just slow to file their updates, which in this case is in your favor.

They care more about the asset value than your own credit history.

Market rent was about $3,300 at the time, but we agreed to a $5,000/month rent that includes $1,000 rent credit (which was stated on the option contract, not the lease contract). 

If we do everything correctly and we screen carefully (credit check, employment verification, etc.), what would be the worst-case scenario?

That same idea will typically apply to other types of credit.

If your credit is decent then I would utilize your cash as leverage to leverage:1.

Start working on your credit score and research financing options, including FHA or conventional loans.