The reason the list is short is that most technical decisions follow from commercial ones. What the website says depends on who it is for. Which pages exist depends on what you sell. What the advertising targets depends on what you charge and who can afford it. Attempting to make those decisions without the commercial answers produces work that has to be redone once the answers arrive.
None of the four needs to be polished. A rough description of your customer is considerably more useful than a carefully written one produced three weeks later, and an approximate price is enough to proceed. What causes delay is the absence of an answer rather than the quality of one.
Where work has come from so far is the question most often answered vaguely and the one with the most consequence. Word of mouth, a previous employer, a few enquiries from somewhere nobody tracked. Whatever the answer, it describes what is already working, and building on that is nearly always better than starting a new channel from nothing.
Access to what exists means the accounts rather than the files. Your domain registrar, your hosting, any existing website, your business profile, and any analytics or advertising accounts. The common discovery here is that some of these are registered to a former provider or to a personal address nobody can reach, and finding that out at the start is considerably better than during a launch.
Be prepared for the possibility that you do not have some of those, because that is a normal starting position and it is a finding rather than a failure. A business that never had analytics configured has no historical data, which changes what can be measured and when. Knowing that upfront sets realistic expectations instead of producing a gap later.
What is not required is a plan, a brief, or a decision about what should be built. Those are outputs of the first conversation rather than inputs to it, and arriving with a fixed specification frequently means arriving with a solution to the wrong problem.
Content is the item most likely to become the bottleneck, so it is worth flagging early. Photographs of your work, descriptions of your services, and anything with your actual prices in it are almost always the thing everybody waits for, and gathering them in the first week rather than the fourth is what keeps a schedule.
Then expect the demand on your time to be concentrated rather than spread. Positioning, pricing, and deciding who you serve need your attention and cannot be delegated. After those are settled the work proceeds with considerably less input, so the pattern is a demanding first fortnight followed by a lighter stretch.
Expect the questions to feel commercial rather than technical, and to arrive before anything is discussed about tools or platforms. That ordering is deliberate: technical decisions follow from commercial ones, and a conversation that begins with what should be built has skipped the part that determines whether it is the right thing to build.
Gather the access before the first working session rather than during it, because chasing a forgotten registrar login is the most common way a first week produces nothing. A short list of what to locate, sent in advance, converts that from a delay into a task.