What are the ways in which you can get a discount on a prop?

[Joe Henry]

In many books and articles I'm reading that successful investors buy at a discount. However, these sources don't specify how they get that discount. I'm assuming some of the discounts could be:

1. 1. Property needs sweat equity work, which could be counted as a discount disregarding your own time value.
2. 2. Motivated sellers. You hear of the rare cases when someone wants out fast and is literally willing to knock 20% off the price.

What do you think people mean when they say "only buy at a discount of 20%" and things like that, and are there any ways I'm missing that you can get a discount?