How desirable is the neighborhood; will you have a hard time trying to resale?

I hear your emotion in your post and the desire for satisfaction in "righting this wrong." 

What would be more desirable to you and why, 3 duplexes on one parcel of land or 6 units in one building on one parcel of land?

Have you run the numbers on your primary home to know whether it will cash flow at all, or meet your desire for it to cover some part of your new mortgage?

That's great, so long as you are local, and still have a desire to be an active participant in your rentals. 

What is the best/most effective way to invest in real estate if you are a person with access to capital, but no desire/skills to become a landlord yourself? 

This is an incredible new loan structure in my opinion, enabling a lot more people to understand and act on their desire to buy and renovate. 

I break it down into four steps:StrategyAccumulationPay offRetirementGoing to #2, how many properties do you need to accumulate so when they are paid off you have your desired cash flow?

The co-signer request is coming from the lender and the developer feels like it would also be asked for by other lenders, the terms on this one are good, and there's no point in starting over on the loan only to end up with the same result but a different bank (and possibly less desirable terms).Again, I don't have a strong sense of what I should ask for in return for playing this role if I decide to move forward and how my participation might be structured.  

Worth & Arlington you suggested is what price are you willing to pay for the property, what rents your seeking, and what is your desired cash flow at the end of the day?