I have done a little of both.
We had a client that was building a vacation home in another state. He hired me to be a "construction advisor" for the sitework and landscaping. I visited the site about a dozen times during the wntire process. I was his set of eyes for that part of the project.
I have also done many "prescriptions" as I call them. I have got many a call for an estimate, and the only actual reason was that the customer wanted some free advice.
We will make a site visit, and prepare a "prescription" for the maintenance, complete with schedules, material lists, work instruction details... We can also make visits during the progress of the work.