The job market in the modern era is very different from the one of twenty, thirty years ago. There are thriving professionals in today's industries who have not actually held a "job" in years. So, not technically being "employees," temps, freelancers and day-laborers bring with them workers compensation insurance questions that aren't always easy to answer, but we'll do our best:
Temporary Employees: The primary responsibility for your temporary employees falls on the agency that employs them. They may be working for you, but they are employed by the agency and workers compensation concerns will generally fall to their end. That said, this is not a guarantee against being sued. Client companies can be sued for a general liability claim. To avoid this, you can require the temp agency to take full responsibility for any injuries their workers suffer at your place of business.
Day Laborers: Assuming you have hired day laborers through an agency, they count as temporary employees, and everything discussed above applies. Otherwise, they are being hired as private contractors or freelancers, discussed below.
Freelancers: A freelancer who wants workers compensation insurance will be required to buy it for themselves. However, this does not mean that you are completely off the hook, should a freelancer or contractor be injured in the course of performing the work duties with which they have been tasked. If someone is injured building a fence for you, for instance, they may be entitled to sue you for damages.
In short: You need workers compensation for your actual employees, the people that you have hired through interview processes and provided with benefits and a steady paycheck, and you need general liability for everyone else who works for you.
It is worth understanding, of course, that just because you hired someone on a contract basis, that doesn't mean that the court will regard them as a contractor. The rule of thumb is as follows: If the payer is commissioning the results of the job, the worker can be considered a contractor. If the payer is dictating how the job is to be done, they might be regarded as an employee. Additionally, you may incur further liability if you attempt to instruct your contractors in the task and they are injured as a result of following your advice. So, it's a good idea to just stay out of your contractors’ way.