In Texas,
The only requirement is that you be a certified EMT-B. There is no experience requirement.
Class are often 2 nights a week for a semester for EMT-B, or you can take it in the summer and get it done in a month or two, especially if you don't get it for college credit, but with a fire department or EMS service.
Once you begin the paramedic program, it is in 2 phases. First, you do the EMT-I phase, which is a semester. Classes are often 2 nights a week. At the end of that semester, you can become certified as an EMT-I.
You then begin the paramedic program, which is 2 semesters, again with the 2 nights a week class. If you do the entire EMT-I & EMT-P program, it is often August-August, so 1 year. This is if you are only going to classes a couple of times a week, thus allowing for you to go to college full time as well.
If you are not an EMT, you can start the EMT course in the summer, and then finish the entire paramedic program by the next August.
Try to become a member of a volunteer EMS service, even before you get certified, and they may pay for all or part of your school in return for your service.