website having a good niche, domain should be based on niche and Google Keyword tool high ranking keyword, having good traffic, and building a active social network will sum up a good website with higher value.. PNP4All
You can find this on your own, on usually websites being sold for on flippa.com, which is a buy & sell place.
Just focus on good content and backlinking daily. Websites that are making money on autopilot sell on Flippa really well.
When you say it like that, just also add onto the additional skills it requires to those things you mentioned. 1. Do you know what a link is? How do you create one? 2. Have I done a proper keyword research? You get the point, theres so much to do and this is why most will get lost.
Independent of niche I noticed that sites with unique graphics, some functionality like ,e-commerce platforms or WP plugins, or even "gimmicks", like an interactive flash app,sell easier and for more.