Investing in Duplex that needs roof and siding repairs

[Spencer Wagner]

Hello BP Members!

I'm trying to analyze a deal on a duplex 3/2 unit and 2/2 unit. The home was built in 1974 and needs some exterior work (not the kind that adds value to renting). It looks like it needs a new roof or significant roof repair as well as wood siding repair. What's the best way to estimate the cost? We are house hacking, so our return won't come from our renters alone, we will be fronting the cash. 

The list price is $215k and rents in the area range from $900-$1300 I crunched the numbers and was thinking of presenting two different offers. One at full list with the roof repairs completed, and the other for 20k less and I would take care of the repairs myself. 

Any thoughts? Have I analyzed this the wrong way?