@Janette I saw your message, and see that you've received a number of replies to your OP.
I am a huge fan of illustrators understanding the concept of Work For Hire (WFH), and then based on that understanding, deciding if they wish to agree to it or not for a given project.
I encourage all illustrators to read and understand the copyright law in their given country. In the U.S. it is Copyright Law of the United States (Title 17)
An important concept to understand about WFH is that when you agree to transfer your copyright the client now becomes the legal "author" of the work. From a legal standpoint you did not create the work, the client did. The client, as the author of the work, had no obligation to give you a credit line. The client now controls ALL the aspects of copyright, including the sole ability to distribute and profit from the work for 95 years after it is published (or 120 years from date it was created)
Work For Hire is a very specific term that is defined in Title 17. Check out Section 201, subsection b.
I briefly explained during the conversation that the illustrator maintains the copyright of their work, but sells the rights to use the images to the author and it would be laid on in a contract
Fundamentally correct, but I would encourage you to alter the word "sell" to "license".
"Sell" implies a transfer of ownership. While "license" implies renting the rights to the client for a limited amount of time. Check out this article from the Graphic Artist Guild To Sell or to Rent: The Difference Between Copyright License and Transfer
As I understood if, work for hire means that you have benefits and are basically an employee.
Yes and no.
It is true that most illustrators who are full-time employees of a company have signed a WFH employment contract with the company they work for. But legally it does not HAVE to be that way. That is, there is no specific U.S. law that says: "All work created by full-time employees MUST be created WFH". It is simply much easier (and potentially profitable) for the company to own all the intellectual property created by their employees, during work hours, on company property, using company tools and materials provided and paid for by the company.
But in theory if the company wanted you and your creativity badly enough you could say that "Everything I make every second Thursday of the month is not WFH. I license that work only for the time that I am fully employed by the company". It would be unusual, but not impossible.
My feeling with full-time employment and WFH is that it is a reasonable trade off.
As I mentioned earlier as a full time employee you make work from 9-5. At 5pm you stop working.
You make artwork in a building the company pays rent on. The company heats and cools. The company provides water, gas, and cleaning services. You work on a computer the company buys, uses a phone and phone service the company pays for etc. etc.
But most importantly, if you come in to work one day and there isn't a project for you to work on -- you still get paid an hourly rate and get insurance and benefits!
For all this the agreement is: all the intellectual property (IP) you created during the 9-5 you are in the company's building using company supplies, the company owns the IP.
Now, when it comes to freelance my opinion on WFH flips completely.
All that stuff the company pays for, well as a self-employed freelancer YOU pay for everything.
If you come into your studio and there isn't a project to work on -- you don't get paid that day. Oh, but you still pay for all the materials, utilities, insurance etc. etc.
There is little to no reason for a client to need to own the copyright to the original IP a freelance illustrator creates. As a freelance illustrator I personally recommend maintaining control over all your copyrights, and only licensing limited, specific rights. Licensing the client specific rights for a specific amount of time will allow both the client and the illustrator to be successful.
Of course it would be easier and more convenient for the client to own the copyright to your illustration (IP). And the only way for a client to own the copyright to your work is for the illustrator to sign (you can't do a WFH transfer verbally) a WFH contract. But like all things that are convenient -- a WFH transfer of rights is, and should be, extremely expensive.
I think of it (roughly) like this:
A pie company is just starting up. They want to deliver those pies to clients all over the city, but they don't have a delivery truck. They do have a small budget to rent a truck for a week. And in that week ideally they will generate enough money to make more pies and rent the truck again to deliver them.
Yes it would definitely be MUCH more convenient and easier for the new pie company to own the truck. But buying (WFH) a delivery truck is very expensive. Renting (licensing) the tuck successfully accomplishes what the startup company needs right now to be successful.
This analogy is imperfect because a vehicle loses value with age, while the more an image is promoted the more valuable it becomes -- but hopefully you get the idea.