As you noted a good front tine tiller will do the job, although a 5 HP
model is a little light for breaking up Bermuda sod. The rear tines
jobs are a bit more stable and easier to use. To tear up sod or till
any ground that has debris, the forward rotating tine models are
superior. The counter rotating tine tines run smoother, but they tend
to pack the debris up under the drive axle clogging up the machine. If
you are only going to do 500 square fee, you will be way ahead to hire
someone to plow/till for you. You will not need much size in a tiller
to maintain a garden once it is broken up. Another alternative would
be to rent a tiller in the BCS, Troybilt Horse class.