Ok, so Im currently seeking employment. I have my degree in Marketing. Unfortunately there are so many "marketing firms" out there that are scams! They are nothing but multilevel marketing, pyramid scams. Are these questions inappropriate, to ask before even wasting the managers time or mine. Lots of these questions should already be on the company website, but aren't.

1. How long has your company been around?

2. Who is the CEO?

3. What is your business structure?

4. After reviewing my resume, which enabled you to get familiar with my skills and qualifications, would the position I'd be interviewing for be base Comission, or 100% comission?
(the reason I ask is, because I will just get calls that say to come in for interview but NO specific job title is descibed. Even on the website there is just a link to send resumes)

5. Is it field work?

Now the salary question, I am NOT asking for numbers. Just if its base or comission because a lot of job posting say "base" or "comission"
All of these questions are reasonable for ANY position. If someone has a website without job descriptions, DO NOT submit a resume. It IS a scam.
You should also consider NOT looking at marketing firms. As you say MANY are scams. Many, if not most companies have a marketing DEPARTMENT. Look into marketing departments of companies you KNOW are legit. This is also good means of finding legitimate marketing companies. Ask know companies if they use an outside marketing company and if so, which one.

Edit: Dennis: if you think these are inappropriate questions, you probably work for minimum wage. Knowing these answers before you interview actually HELPS in most companies. It shows you actually CARE about where you apply. If MOST of this information is not on the companies PUBLIC website, the COMPANY is suspect.
WOW!! Impressive! Someone who understands that the recruitment process is a 2-way conversation/evaluation. You have ever right to fully understand the company you are considering joining and if is a legitimate firm they will be happy you did - if you accept the job, there is more chance that it will end up being a good fit.

Q4 - I would rephase and ask something more general like "what is the compensation structure of this position"

Good Luck!!
Those questions are really inappropriate and I think you will never get hired if you insist to ask those questions to your employer. YOu should ask those questions.