As the age old adage says " you make money when you buy real estate, but your realize it when you sell".
Before you make an investment for purely appreciation in a short period of time, contact a good local broker and discuss the transactional expenses that are involved with both the buy and the selling ends of the transaction.
By the way, there are very few co-op opportunities on the North Fork, and there are a fair bit more condos in the market.
Please keep in mind that for many buyers, there are returns that can not be measured in terms of dollars !! Enjoyment of the East End at your own schedule, relaxing and going to our many beaches and fine restaurants , or just relaxing in front of a fire and reading a good book !
Good Luck, and be sure to contact a knowledgable local broker !
If you want to keep yours in line with the others, keep or bring it up to the condition that others have.
Not keeping it up or leaving it as physically distress will bring the property down close to those in the same condition, with less value.
So it depends on... how much you bought the property for, and what kind of condition it is going to be in in a year's time.