Suggestion: Rent the highest level trombone that you can find. You may decide to change to a bass trombone -- I did in high school. You may start doubling on another instrument for jazz and change over. (Did that in college.) Renting keeps your optio...
I played bass trombone for 3 years and found that it is extremely similar to a tenor trombone slide. Play with a tuner to find out for yourself. If you are a beginner or intermediate player you may not even notice any difference.
e-mail me at and I'll give you a quote on a similar trombone.