Everyone else has mentioned the noise but I'd also be worried about water leaking from the top unit into the bottom unit.

Because you are in that High Opportunity zone there is a significant jump in rents, and it is often higher than the market rent in many zip codes.

Hey Robert, high appreciation will bring you the biggest returns. 

We are already a fortunately high net worth family. however, that is from my spouses W2 income, so at this stage we don’t really have anything tangible to “leave behind” and we want to try to build generational wealth for our child. 

I am asking because construction cost right now are pretty high.

If you're attorney is smart and honest with you. ( that's funny).A couple letters showing scare them out.I  have other ways but won't say because everyone will get mad but tenant will leave quickly. ( stop paying water bill).

You can deduct a proportionate amount of your mortgage interest, property taxes, insurance, electricity, water, gas, etc. and you can deduct any expenses that are directly associated with the portion of the property that is being rented out.

Interest rates are high today, but do I wait and buy when rates drop or wait when prices jump? 

I would highly suggest that you also get involved in local real estate meetups.

For most of us, that situation would be a year of very high profitability.