I'd like to hear how you "improve" a website. I assume you bling it up a bit (fix any obvious design or navigation problems, pretty pictures, beef up the call to action, etc) and then you work to boost the site analytics (SEO, drive traffic with ads, increase the sales figures, that sort of thing). Same whether you're flipping it or developing it to hold as an income stream. Am I missing anything?
You don't have to completely overhaul a site to make it more profitable. It can be something as simple as changing the location of one ad, selling a banner to a company for a monthly rate, adding some affiliate links that convert, etc. Adding $100 in net value is actually pretty easy. There may even be an operational expense that could be changed to save that much. I changed hosting on that Flippa project and saved about $100/month.
Of course each of those activities entails a whole list of skills that a newbie is unlikely to have. Some of them (like spiffing up the website) require web-coding skills or hiring someone to do it. Are there any good educational guides (like @Aaron_S's FE Intl pointer) that could give a newbie a step-by-step guide to the other parts? Or is this a "barrier to entry, go figure it out yourself" thing? Googling "flip websites" returns lots of possibilities, but does anyone have a particular recommendation?
There are case studies and tutorials out there but depending on what industry and business type you select the studies may or may not be applicable. Here is a good study on a niche resource site that is only a couple of years old. That site was already setup in Wordpress so the technical skills required were minimal.
The other question I have about buying websites is the longevity. The website has to continue to throw off income at a steady rate for a year or three just to earn back the purchase price, let alone the cost of ads, improvements, etc. How stable is web income? How often does Amazon or Google change the rules and destroy your income model? How hard is it to keep a steady/growing income stream in the face of constant and growing competition? These are things that you really need to understand in order to make an informed buying decision.
With a flip you don't neccessarily have to earn back the purchase price by running the site long term yourself. Just like a real estate flip doesn't need to turn into a long-term rental before it can be flipped. Web income can be pretty stable if the sources are diversified. The same as the previous sentence if Amazon or Google are the sole income and/or traffic sources that is risky.