Is it enough to just get a signed lease for that rental income? 

Assuming you have good income/debt and good credit, you should be able to get another mortgage.

You separate the holding company for a number of reasons: rental income is taxed at a some of the lowest rates, and the risk of loss is different in character than that of running operations, its tax filing looks different (as a business) than a business that runs operations (deducting capital improvements, etc.), among others. 

Typical SFH lender guidelines allow for (75-80%) leverage on properties and consider your debt to income ratio. 

I have plenty of wealth in investment accounts to cover the purchase, but I'm trying to maximize my passive income, so I'd like to leverage a mortgage using my current income to pay for as much of the property as a I can.

If you keep track of mileage for income tax purposes you should get a PO Box as close to home as possible.

I'm working to develop a stable, and passive income through real estate.

You have to be Accredited to invest in DSTs by the way - $1m net worth excluding your personal residence or alternatively you meet certain income requirements.

Annual numbers are:Built in 1984 - Seems to be a B class complexPotential rental income $900K-$1M gross6% vacancy ($60K), $20K addition income from vending/laundry - no other amenities, $65K taxes, 5% ($50K) Capex, $28K Insurance, $16K contract services, $90K payroll/staffing, $150K repairs/maint, $6k utilities (tenants pay their own), $10K accounting/legal, $5k advertising/marketing, $100K (10%) PM (is that redundant with staffing?)

My partner has a steady job and indulges my lifelong passion for passive income.