I just purchased my first duplex (only SFHs in my portfolio so far) and it doesn't have the gas/water split.

You might consider hard money for the initial purchase or going with a DSCR type lender if you find something that is more turnkey.Hey!

Since then, I've purchased 7 properties in my local area.

I'm not a fan of novations where you don't get the purchase agreement notarized and filed at the courthouse.

Quote from @Enrique Toledo: I came across a really good seller financing deal and I would like to purchase it as my first deal but I don’t have enough money for the down payment.can I use a lender of some sort to give me money for the down payment?

I’m looking to raise $160,000 to cover the purchase, renovation, and activation of this new Airbnb property.

The property is being purchased at 103 with an ARV of 375.

What if I told you that you could purchase this property at 20-30% of the initial price, would you take that deal? 

If you're looking at a debt service loan, 15% is the minimum for a purchase but it's much more common (and rates are better) at 20-25%. 

Yes you can find properties which you will be able to purchase, but ROI will be near zero or negative.