The proper identification is an entomologist, which is a person that studies insects. However, if you want to be very technical, a person that collects actual bugs, which are a type (or class) of insect, that person is called a hemipterologist.
A bad person. Unless you buy it and DON"T liKe it that's when you return it or sell it.
A person who buys a lot of things is often described as a shopaholic.
An author is a person who writes and sells books.
The person who sells drink is known as sellsmen
A realtor or estate agent buys and sells real estate on behalf of the principle, for a commission. They can also act as a managing company on behalf of the landlord.
baker
A person who sells books is commonly referred to as a bookseller or a book vendor.
You call a person who sells flowers a (Florist)
A person who sells ship supplies is called a chandler
A person who sells jewels is called a jeweler.
fishmonger