Is it possible to hold wort in a sanitary condition, ie.. for a few days, and boil it at a later date?
What's your definition of "a sanitary condition"? Your wort and beer can never be any better than the weakest point in your process.
Wort separated from the grain and pasteurized to 165F, then rapidly chilled to <45F and kept anaerobically or under vacuum can have a stable shelf life of about a week. Higher temperatures can extend the shelf life a little.
However, wort has a lot of compounds in it that will change, regardless of sanitation. Even fully boiled, canned wort will oxidize and change pH. This isn't bad for canning starter wort, but a whole batch may become lackluster, at worst create a permanent haze and other redox flavor issues once bottled.
Malt extract is notorious for oxidizing, darkening and developing issues that show as underattenuation and "twang."
As with beer itself, wort is best when fresh.