Cleaning my portable toilet. Is it better to clean on my own or rent a porta potty rental company to clean the restroom.

Depends in my opinion of where it is being used and I am speaking here of making the inside of the toilet sanitary, not the removal of the actual waste which was always done by the supplier/leaser. We used them for construction field offices and sometimes the construction contractor (who had to pay for the service) would clean with his own forces. Others would sometimes have it included and done by the toilet supplier.
We preferred the contractor doing it with his own crews because it was cleaned when it needed to be cleaned, not just on a set schedule.
When the supplier cleaned them they would typically spray the interior with chemicals from top to bottom and often leave surfaces wet and sloppy. Users had to be careful to dry off surfaces etc.
It can work either way but if you consider having the leaser clean them, get some details on frequency of cleaning, how the toilet will be left etc.
If this toilet will be used near food sales, health dept. rules have to be checked into also.