BE$T bang for your buck home improvement for home sale

Wife is a realtor. Simple answer is bathroom. We have a customer that buys rural homes to remodel and flip. He does well IF the floor plan and outside appeal is good to start with. You can not put lipstick on a sow, and make her pretty! He over paid for a 10 ac tract with 2 houses on it, built feet apart. What a cluster f*** Still for sale 2 yrs after and dropped the price 3 times!!!!!
He bought another one a nice well laid out home They remodeled it with granite counter tops, nice everything, BUT then they did not finish some mouldings that would have cost them $5-600!!!! On a $330,000 price tag what is $600 !?????????? Go figure.
Most of what she sells is country property. I hate houses!!!