Your debt to income ratio will get again to a point where lenders will be confident lending you money again.

If you want to forecast returns based on your confidence in price appreciation and income growth:IRR - FORWARD-LOOKING. 

And yeah, I can imagine the seller needs to feel pretty confident that you've got him covered!

Well, talking to him gave me enough confidence to make an offer on the 11 unit.

Once you have the resources (money, team, etc) and confidence execute on your own.   

Assuming your reno budget and ARV are correct, you want to get this for closer to $40k.How confident are you in the expected rent. $1200/month for a $85k house looks high, but I don't know anything about your market.Closing costs look low.

Of course I’m not looking to get rich on this deal, I know small risk is small reward but I think it would be a great stepping stone and I want to take on a small rehab property as a learning experience to gain confidence for bigger deals that need more work. 

If you don't, or you're just not sure, hire a property manager until you gain some knowledge, experience, and confidence.

I'm comfortable with my understanding of the metrics, what they mean and how to calculate them but where I lack confidence is knowing whether the particular numbers are "just ok", "good enough" or "great".

Unfortunately, what that says to me is that they do not have confidence in the underwriting ability of the lenders, which in turn means the end consumer gets to pay for this lack of confidence or the lender's inability to properly underwrite.