Less relevant to the sales process than to general organisation, but one thing that occurred to me to be worth sharing is to keep good notes on your research.
I recently took a domain off the market when I wasn't able to get what I felt was a decent price for it, and put up a small site on the domain to get it ranking and pulling in traffic (the idea being to have some data to back up the value once I put it back on the market.) The site has been up for a little over two months, and has generated affiliate revenue equivalent to 20% of my original asking price for the domain. It is not inconceivable that by the time it's been up a year, it will have brought in at least 50% and perhaps as much as 100% or more of the price for which I was willing to sell the domain originally.
What does that have to do with keeping notes? Well, when I was sourcing my end users, I was making notes of top advertisers for the keyword, top organic search rankings, related search terms etc. all of which made generating the basic look, feel and initial content of a site very simple (by emulating what was working for others.) Very minimal work and essentially zero expense went into the site. If you have the data and don't have the buyers, that does not mean the data is worthless.
Frank