There are three additional large economic drivers in the area as well.

33 Unit - Asking $4350000 - ( I believe I can offer $4120000)Building is %100 occupied Current Rental Income -   $400380Total Additional income  $20698ExpensesReal Estate Taxes $66,695Insurance $8,407Trash $3,534 Electric $2,375 Alarm Monitoring $666 Gas $18,749 Pest Control $1,135Water/Sewer $24,051 Landscape/Snow Removal/Cleaning $12,168Management $34,439  Repairs/Maintenance $16,000Cap EX $20019                        TOTAL EXPENSES $208235NET OPERATING INCOME: $212843Dept service  $195600There is a big rental upsideCurrently the average rent is 1042 per unitComps tell me that if I fix up units @$8000 per unit - I will be able to get $1300 average on a unit.Once all units are done over the building should be able to fetch $6m after 36-48 months 

In addition to our primary residence I have one property that is owned by my self-directed 401k, and another rental property. 

I would suggest you do a bit of additional homework prior to taking on New Development projects.

The second unit it occupied by Section 8 getting about a $400 discount but she will be only staying 1 additional month after closing.

I did some additional research and found that Fannie Mae’s requirements were 6 months.

I add additional profit for the estimated time and difficulty of the project.

In addition to the mortgage, property taxes, and insurance, the projected calculations are taking the following expenses into consideration (5% rate for vacancy, 5% for repairs/maintenance, 5% for CapEx, and 10% for property management; otherwise the income figures would be higher. 

I have a duplex I own free and clear, and just need some additional money to finish rehab.

How do I handle the rehab with renters in the house or is it advisable to let their lease end and have them vacate before I take on the rehab (since the additional bedroom and bath would be for a new tenant anyway?