Two important considerations are if it's a cash deal and if your intent is to rent or resell.

On the other hand, a cash-out refinance of your current duplex is another avenue to explore, albeit with considerations such as the risk of losing your low 3.5% interest rate and increasing your loan amount and monthly payment, thereby reducing your current positive cash flow.

Maybe a purchase or two from them as consideration.

What unique considerations might there be?

Buyers agents rarely took into consideration the actual buyer. 

There are several considerations that can go into the analysis of whether you need an LLC or whether a large insurance policy will suffice.

I'm not sure if it's possible in my situation, because I know that you need to be self employed for at least 2 years to be able to get a loan, and I don't know if the lender will take into the consideration the money that I have earned before turning 18.

We own over 600 apartment units in Cleveland Heights, Lakewood, and Mentor OH, of which quite a few require rehab to bring to market rent.We struggle to find enough contractors for this work.I know that this is a common problem, but if anyone has any recommendations for contractors in that area, that would be awesome!

I've been burned a couple times early on, but the type of personality that operates with no consideration of anyone else but themselves is easy to spot with a little experience.  

Taxes are also always going to be a consideration, and this is an assessment year, so you should account for them going up more than usual in your projections.