The answer to this depends so much on what point you are trying to make:
Adults get more out of college than younger students (due to experience, maturity, etc.)?
Adult minds are no longer flexible or robust enough to fully benefit?
Getting a college degree later in life will/will not improve job prospects.
You might want to visit the link posted below for a little data and a discussion of the myths and advantages of adult college attendance.
When you say "persuasive", I believe you want to write an essay in which you want to persuade people that it is good for adults to return to college.
Any essay of this type will have two main type of arguments. First type of arguments will present advantages and benefits of adults resuming college education after a considerable gap of time. The second set of argument will counter the argument that others may advance to oppose the idea of adults education. These are the disadvantages or limitations of adult educations.
Some such benefits and limitations are listed in answer to your question above. You will need to expand this list and also collect more details. For example, can you collect some concrete data on the efforts and cost of adult education versus benefits in terms of better job.
To help the readers your essay may contain supplementary information on what types of courses will be best suited for adults returning to college. If you decide to do that, you will need to collect information on that also.
I suggest you start your work right away, and as you encounter problems, you can post additional questions on enotes for further guidance.