Most potential for growth? The Hudson Valley. I have lived in the HV my entire life and can share with you some of the most popular vacation home locations.
My personal favorite:
Cragsmoor, NY - 90 miles N NYC, lots of NYC weekend-escapees ($$$) [Ulster County]
Also:
New Paltz, NY - 80 miles N NYC, gorgeous views of the Catskills to the west [Ulster County]
Northeastern Dutchess County is also worth investigating - Millbrook, Amenia, Wassaic (90 miles N NYC)
Same for western Dutchess County, along the Hudson River - Red Hook, Rhinebeck (90 miles N NYC)
If you prefer a place closer to New York City, check out:
Orange County - Pine Bush, Warwick, Cornwall-on-Hudson, West Point / Storm King
Putnam County - Cold Spring, Garrison
Rockland County - Stony Point