Will Rogers said, "I only buy stocks that go up, they do not go up I do not buy them."
You have two questions here, should you pay cash or take a loan? If it goes up you should take a loan, if it goes down you shouldn't.
My best guess is that it will go up. Nobody knows.
Your 2nd question. How much down?
Most land loans require 35% down. So you probably will need to save some money. Here is a better idea.
Buy a home that is in need of work or the cheapest one you can. you can tear it down and your electric and sewer will already be in, which will save you thousands and thousands. You will be able to buy it with much less money down.