Agree, very dependent on the specific job and they will tell you that; sometimes its on the job description. It might say travel required (could be very little). 25% travel, 60% travel. 25% travel typically means one week every month. I have found that domestic travel is much easier on your personal life than international travel. International usually means longer trips and the time difference makes a difference. There are lots of marketing jobs with no travel though if that is what you want.
Traveling is awesome. With the exception of a few careers, usually your company and your position within will be the main factors on how much you will travel. My advice is search for global companies to work for. If you work for a company with a world wide presence and possibly a global headquarters there is a much higher chance you will be able to travel.
Additionally, as soon as you get into a global company, tell them your desire to travel. There a tons of people who have families that do not want to travel, so making it clear that you are interested in traveling is important.
This answer will vary greatly from company to company and from role to role. Some mar-com jobs you will not travel at all (unless it's for company annual meetings, etc) while others that are more sales or client-based may require some travel. Whether it's something you are interested or not interested in having as part of your role, it's clearly important to you so when you look into job descriptions, make sure whether they indicate whether travel is involved. And always, always ask during a job interview "Will I be expected to do some traveling? How frequent and what types of locations?" to help you understand what the demands are.
This really depends on your role. If it is critical that you visit the field to gain insights, this may require some travel. Typically I would say that most of your work will be from your home base location.