@Tommy Johnson
I read your post. I'm gonna share with you my opinion. I'm going to try to clear a bit your thoughts...
"Hi, so I am in the process of rehabbing my current rental property in hopes of doing a 1031 exchange." I'm assuming, since you said that you have over 200 K equity, the value of your current rental would exceed 325 K, so you'd have to pay taxes on the difference. Also, the seller (and buyer) would have to be willing to accept your offer as a 1031 exchange.
You don't give much info about the purchase of the duplex: cash needed upfront, terms,time.
Your current rental... is that a new purchase and fix up to rent? You say it could be rented out, so, I'm assuming at this point it isn't. Your "mortgage and everything is under $900" . Do you mean PITI is $900?
What shape is the duplex in? Did you get a chance to look at it? Beside the purchase price, how much cash you'd need to invest to make it rent ready? What is the condition of the unit with the section 8 renter? Would you purchase the property, contingent upon, completed and successful eviction? How motivated is the Seller? You got a lot of due diligence in front of you. Once you got all in place, you could make a much more educated opinion as to your ROI.
I, myself, would like better numbers... a lot better. Plus, you said you're interested in a Multifamily. In my opinion, complete the rehab, rent it out (those are great numbers), get a HELOC and use that to purchase a Multi that makes sense financially for you, and is, also, the way you want to go. But, I emphasize, that's because I don't know the terms of the purchase you are considering.