Current operating income, with the vacancies, is $110,000 annually.

If you're a landlord, you may want to check out the Rental Income Podcast with Dan Lane.

Is it truly "passive income" if you find the right PM or is there always work to be done by the owner?

Also, even if the previous owner only owed 60k, you have to take into consideration the cost of foreclosing and the lost income if they hadn't been paying for months or years, not to mention any other costs of satisfying tax liens or maintenance issues that need to be resolved before sale.So, speaking as someone who has bought only 3 foreclosed properties:  You make an offer that works for you, and depending on how anxious they are to sell it, and how much interest they've had, they will accept or reject.  

On the flip side, if you put systems in place for effective management and screen your tenants thoroughly, you can very well supplement your current income with consistent cashflow. 

I've got excellent credit at the moment and a job with six figure income (however much lower after taxes/student loans/primary mortgage), would this help gain what I want with a lender?

(Bob Bowlng is correct that  fourplexes are valued on sales comps as opposed to income approach.)   

Rental Income from other real estate holdings may be considered Effective Income if the documentation requirements listed below are met.

My Father passed away and so my Mother gradually liquidated the properties.As of two years ago I bought my own 4 unit building and live in one of the units.

Unmarried with a salaried income of $38,500.