Buying cheapest land.
What are you doing with the land? Does it need vehicle access? How many acres? Wooded, cleared, water?
Using it for recreation. Looking for 5-10 acres doesn't need to be cleared. Looking for it to have streams and vehicle access would be nice but not necessary.
I think Craigslist is your best bet! Especially in counties that are struggling. I see several pieces of land that fit the bill in Sullivan county on the Catskills craigslist.
You best bet would be to look for over the counter lands available as well as lands available for taxes. When a tax deed property or land was not sold in auction they tend to still have the property available for sale through the county and you can purchase it for the minimum bid amount and have that property free and clear.
I recently went to the Ulster county tax sale. Some decent parcels went for $500 and up range. ( 1 acre and up ) .
The $50 and $100 parcels were pretty bad this time.
There are several websites out there; landwatch, landhub, and landmodo are a few. But, do your due diligence. Consult with a local forestry official or some from the county tax office. Make sure you understand why theyre selling.