I think it's more human problem. Most of the buyers will try to create their own profile. So every time when owner starts his Netflix, it will take him to page "Who's watching?", where most of the people will notice new profile. And most of the time people will create it something like "Mike" or "YOUR MOM IS CUNT". Even if they will try to hide it and create something like "Kids" or "+ Add Profile", it's not really effective since Netflix is not supporting custom profile photos anymore.
Even if they are not creating profile active Netflix owner can notice that it was used by "Keep Watching" or by "My List".
And finally every time you login Netflix sends email saying that there is new login. Regardless to country. Even in the same apartment you will get this notification. And when person buys account he will login in all his devices: on his phone, on web browser, on Smart TV, etc.. And for each login owner gets email, so risk of detection is increases.
Probably best way is to avoid selling of it. Or if you still want to sell it, sell your own account. Get Netflix from Turkey for about 3$. Create 5 profiles, and sell it for 2$ each with one month warranty. 7$ profit from one account monthly.