出張 and 訪問: business travel and visits
Distinguish travel away from the usual workplace for business from a visit to a person or place.
Travel for work
出張 is read しゅっちょう and means traveling elsewhere for work from the usual workplace. 「来週、大阪へ出張します」 says that the speaker will go to Osaka on business next week.
「日帰りの出張でした」 means that it was a same-day business trip. 出張 does not require an overnight stay; the work-related purpose is central.
Visiting a particular person or place
訪問 is read ほうもん and means visiting a person or place. 「取引先を訪問しました」 means that the speaker visited a client or business partner.
It can also refer to a personal visit, as in 「友人の家を訪問しました」. 訪問 alone does not establish a work purpose or a long journey.
Visits within a business trip
「出張中に二社を訪問しました」 says that the speaker visited two companies during a business trip. 出張 refers to the overall work-related travel, and 訪問 to the visits within it.
「訪問の予定はありません」 says that there are no visits planned. It does not mean that the business trip itself has been canceled; preserve the target of the negation.
Does 「出張先で友人の家を訪問しました」 establish that the visit to the friend was work-related?
Show the answer and why
No. It only says that the speaker visited a friend's home at the business-trip destination. The purpose of that particular visit is not specified and should not be inferred from the trip's overall purpose.