Make sure you budget for extra holding costs as you are bound to lose some time with permitting, inspections, etc.

Does it permit assignment?

It seems that duplex is permitted. 

The day after rent is due issue the pay or quit notice, apply late fees as permitted.

It would not be bankable at that price because it will not even make the appraisal and will not meet the coverage ratio on the debt more than likely.The extra land to expand story is as old as the industry has been around, and means nothing without an actual permit to build in hand, and even then you will need to price it out (around $20,000 per lot plus land cots plus tap fees and engineering).I would price this deal more at around $550,000, which is a win/win for both buyer and seller (assuming you can still push rents based on market).

We got permits for the egress windows.

Meet with the permits department prior to closing and consult with a architect.

Whether it's extreme rehab, quick closing/cash offer because seller needs it gone, or risk due to area/permitting/market timing

I also bought quite a few 20 40 80 acre tracts and would bust them up as well.. it was pretty cool because in Oregon logging permits are a snap.. you dont need any county grading permits to bust in your logging roads so say I had a 20 acre that I was going to short plat into 4 5s we would put the road in the logical spot for each parcel future access and then put a few landings in the logical spot for the homesites all under logging permits saved THOUSANDS .. then sell off the lots..

Newcomers usually do less than 20% and get to 20% once you got a couple of deals under your belt.