Quadruplex deal, negative equity, good cash flow

[Jai Deva]

I am interested in a quad. Numbers below: 

Asking price 120K

Total rent: 2150/month

Expenses: 

P&I: 483 (5% int rate, confirmed with my lender)

Insurance: 100/month (not confirmed yet)

Management: 215/month (10%)

Taxes: $80/month (county office)

Cap ex - $107 (new roof, new AC)

Maintenance: $215

Other expense: lawn 50/month

Vacancy: 107 (has long term tenants, all four unit rented by same tenants for >2 yrs ) 

Bigger pockets calculator showing monthly cash flow of $791 ($591 by 50% rule) 

The county website also mentions that the property appraised at $66000 last year so it means negative equity, right? 

This is my second buy and hold property but first multi-family. Your inputs are very much appreciated. Thank you.