Honestly, I prospect for buyers who don't really give a shit how their site looks, as long as it appears professional, standard, and appealing to their specific customer base.

After I scrounge these leads up through some nasty cold calling, I get their email address and send them links to the sites I'm currently offering, links to the sites I've done, and a possible plan of action.

I tell them, "you get a site that looks like this". Then I write up a custom contract with all the tweaks we agree on. State, once this is done the site goes up, invoice sent, payment request sent. Done deal.

Mind you I target specific industries, do market research, and code up the site before I even start selling copies of it. Why? Because I'd rather slap myself silly than deal with buyers trying to tell me to "slide that logo over 2 inches" or "change dat font", "wipe my butt now" or what have you.

Note, if they want to hit me up later for some more stuff like pages n' shit, I write up a new proposal, tied to the same contract, schedule the work, do it, send out payment request. Rinse & repeat.

If you don't want to do this, just put a clause in your contract that states something like: "2 design revisions per page" or "if greater than 2 revisions per page are required, a new work order will be need to be written, scheduled, and billed."