I had a similar experience to @Chris Seveney when I got into the land business in 2009. From an acquisition standpoint, it was awesome. It was common to buy land for 10-20% of what it had been selling for just a year prior, sometimes even less. It was the easiest I've ever seen to buy land at a discount in any market I tried. There were a lot of motivated sellers for every property type, especially vacant land.
On the selling side, as you might expect, it took much longer to move inventory. Everything would sell eventually, but I usually had to list it at 50%-60% of 'market value' (what it had been worth before the crash), which meant it was very important to buy it at a huge discount in the first place.
Even when listing most vacant lots at a discount, the average time on the market was 6 - 9 months. If it was an amazing piece of property and/or if I offered seller financing with great terms and I marketed it well, it could sell in 1 - 3 months.
I'm not sure if we're heading into another 2009, because that was a very extreme downturn, but over the past few years, most people I know have been offering a minimum of 40% of market value for land right, with many of them going even higher. This is fine when values and demand are rising, and things are selling quickly. It can also work if you're planning to do an option, assignment, or double closing, because you're not taking on the risk of holding the property for an extended period, but if things continue slowing down (thank you, high interest rates), you'll want to be very careful about how much you're offering, especially if you stick to the straight flipping model, where you take title to the property and don't make any improvements to force appreciation.