I think you would have difficulty booking through an agency as they usually specify 21 as the lower age limit due to insurance reasons.

Same sex groups or mixed groups of teenagers are also generally a big no no as most of these houses are oriented to the family market.

You could try the websites where you rent direct from the owner and not mention how old you are but they usually ask how many people are staying.

There are houses you can rent I am sure that are geared to the sping break crowd – try googling “vacation rental” or “vacation home” and “spring break” as this might bring up possibilities.