This is my first time and I'm buying a fixer upper that needs a new compressor, roof and a total kitchen remodel.

if the roof is halfway through its useful life, then not much to do there. 

Prices are through the roof in this current market with low inventory and single and multi family properties just don't pencil out.

after seeing all the risk management/insurance that comes with tenants wood fire usability, I was wondering the same, or, actually:   I'm thinking to seal the cap on roof and run a cord putting an electric Infrared heater fireplace in there, so they can still open the glass and get heat and watch TV over the mantle, but can't burn anything or have any flame.  

What's the life expectancy of the roof, paint, furnaces, water heaters, etc.?

New drywall, mechanicals, windows, electrical, roof, siding- essentially new from foundation up. 

And take the roof off and build up.

Details on the duplex:Price: $385kBuilt: 2012Size: 2674 sq ft (1333 each side). 2 story, 3B/2.5B each side w/ 1 car garage & driveway for both, fenced backyard both sides.Interest: 5.49%PITI: $2,698Current Rent: $1,350 but could be brought up to ~$1,600, maybe $1,700Yearly Property Tax: $8,340 (I don't pay any on my side while I live there so $4,170)Upgrades: Vinyl floor in kitchen of both units, new AC (central HVAC) on vacant unit, roof done 2016. 

Some reasonable- a roof and ceiling repair from a major leak... some not so reasonable (they literally made me escrow the cost to add a deadbolt to a door).

The need for a home and an office under one roof.