Unsure as how to go forward with seller

[Alejandro B Yoon]

I found a property off-market in the Montopolis area and am about to go to see it with the owner on Friday. The original owner passed at 97 a few years ago and now is handled by a son who is the executor of the will. The executor has 2 next-door similar lots; one with a 50's tear down with no foundation (has a 2-room extension built 30 years ago with foundation) and a vacant lot the same size with an old concrete driveway. 

They are asking for 405k each, which is just over some sold comparables for a teardown on a lot that size (I have access to MLS); they say they have turned down offers before and last received an offer of 350k less than 6 months ago that they didn't go through.

The highest I think is doable for us is 380k and selling the contract for maybe 385ish. This will be my first time so I am not necessarily looking for the highest margin. Newly built properties on that lot are selling for ~700k range so I think that would be an appropriate price for a flipper

I am unsure as to whether I should offer on the teardown or empty lot. As I want to be able to have a strong case to lower the asked price and incentivize a buyer. 

Any and all critique is welcome. I am a 20 y/o agent that works hourly for Redfin and am just trying to wholesale during the summer before my senior year of college. Thank you.