New Construction vs Old?

[Cheryl R.]

I was looking at a duplex, and across the street was a lot for sale where another is being built.  The new one will sell for $330k, rents will be $1500 per side ($3000 per unit).   The one I was looking at is $350k and is older, but has tenants already.  How would you make this decision?  How do you factor in the time costs?  The new one will take 6 to 8 months to build, then I have to put tenants into it...but it will be brand new and I can choose the most durable materials to put inside from the start.  The unit for $350k needs some updating and rents for $1400 and $1500 per side.   The $1400 is a long term tenant and the current owner has records that they pay on time.