From a logical standpoint, it seems like cast iron would be more durable, but I've read stories where the coating chips very easily.

The IRS could easily see this as a transaction by each of you designed to benefit yourself, and therefore disqualified to your respective IRA accounts. 

I used the filter in listsource to show me only buildings that had between 4-200 units that had complete addresses.  

You can easily be distracted with online classes.

Something that can't be easily faked and that won't bounce on you. 

We maintain the habitability of the unit and easily meet the housing quality standard (HQS)  because our standards are higher than that of HUD and the PHA.If a Section 8 tenant veers from abiding by the terms of our rental agreement we have the additional benefit of being able to contact the tenant's case manager at the PHA and they will put pressure on the tenant to come back into compliance.

 A new investor should not deal directly with a listing broker/agent, one side is represented the other is not and you can get your clock cleaned easily.

Maybe you vacate the tenants, maybe you closed in 5 days cash with silly seller contingencies, maybe it's a package deal, maybe you buy it with a title flaw that can be easily solved on the resale.....dozens of things that many buyers can't/won't do.  

Instructions aren't needed, there's little to no question about how it's going to turn out, if my concrete guy disappears, I can easily find another.If I start working with a new product like hempcrete, I have to either find someone who already knows how to work with it.

I own several duplexes in Kitsap county and I've found that I can meet the 1% rule very easily, but 2% is still out of reach for the most part.