You are right to be concerned.
Your safest bet would be to 1st sell your home in the suburbs and then buy the 2/3 unit building you intend to live in and then scout out and investment property. This will give you the greatest freedom and flexibility of choice with respect to the purchase of the property that will become your new home. You'll also gain hands on experience managing tenants. Finally it also helps to tighten up the numbers and give you a clear sense of what you have left in the tank for investment purposes.
For the owner occupied property:
You can finance with as little as 3.5% down using an FHA loan or if you choose conventional (Fannie/ Freddie) financing then the Owner Occupied property will require 20-25% down 20% for a 2 unit and 25% for a 3-4 unit.
For the investment property:
Conventional financing only with a minimum down payment of 25%.
The differences between FHA vs.. Conventional financing and Owner Occupied vs.. Investment properties can be significant. I would recommend you speak with a lender directly. You can lay out all the cards on the table and then structure the best game plane for your individual circumstances. There are simply too many variable to cleanly diagnose in the forum. In the end it may be less about determining if you qualify to purchase 2 multi unit properties and more about taking the time to design a game plan that works best for you.
I hope this helps to point you in the right direction,
