Right now, their gross rents are $4,100, and I can renovate/occupy one of the duplex units for $60k to bump my gross rents to $5,100.

Yep, I usually use 15% of the gross rent as the deduction for V&R (vacancies and repairs) 

If each home will rent for $900/month, thats a gross of $6300.

to analyze a deal i take 50% of gross rent + mortgage + insurance and subtract it from gross rent, if there is money left over the place should cash flow. with interest rates so low it doesn't seem very difficult to cashflow at 10% or even 5%. 

The ideal property would have an ARV of 150-160K in BalCo, generating gross rents of >$1600.

1900s Quadplex (fourplex, 4-unit), (1)2BR/2BA owner-occupied, (3)1BR/1BA, Gross Rent 2640/mo, (2)1yr/(1)Mon2Mon, Electric Separate, Owner pays other utilities, Offer $469k, VA Fund Fee 2.3%, 2.5% rate, 0 down *Currently renting a 2BR/2BA appartment for $1444/moCost AssumptionsPurchase Price$469,000 Land Value (25%)$117,250 Building Value (75%)$351,750 Improvements$0 Closing Costs$14,070 Total Cost $483,070Financing AssumptionsDownpayment0.00%Finance Amt$479,787Downpayment Amt$0Interest Rate2.500%Mortgage (Years)30Mortgage Payment$1,896Cash Outlay$14,070Revenue AssumptionsMonthly Rent$2,640Vacancy Rate3.00%RevenuesRental Income 2,640 Vacancy/Loss Rate3.0%Vacancy/Loss Value(79)Gross Income 2,561ExpensesProperty TaxesAnnual 5,398 InsuranceAnnual 1,956 Maintenance & RepairsAnnual 3,500 Utilities  Annual 3,150 Variable Cost PM(% Income)10%Flood Insurance Annual 1,293Total Expenses 18,370 Net Operating Income (NOI) 12,360Cash FlowNOI (Cash Available) 1,030 Mortgage 1,896 Total Cash Flow(866)CF & ROI (Outsourced Propert Manag.)Annual Cash Flow($10,389)Cash ROI-73.84%Total ROI3.48%CF & ROI (Doing My Own PM)Annual Cash Flow($7,316)Cash ROI-52.00%Total ROI25.32%cap rate2.64%Option to pay $1200(qtr point) to get 2.325 rateIn a desirable Norfolk neighborhood.

Insurance will be another $100/moSo gross rent-utilities-insurance-taxes=NOI?

If your CFBT is better than 5% of gross, I'd be OK.If you're buying it to live in, at DTI of 50%, how'd you qualify? 

It would be a challenge --- albeit a doable one --- if you are looking at it from a gross revenue perspective. 

Gross Scheduled Rent, @Mike Barone.