If you plan to purchase a porta-potty, or a hundred, you are interested in first cost, ease of maintenance, and long-term life. [please scroll down for more information about buying]
You should avoid any porta-potties with chromed or galvanized steel parts, because they will quickly corrode in the atmosphere of a porta-john. Select portable toilets with plastic and stainless steel components only.
Ask the manufacturer for the cost of replacement parts, including the urinal assembly. How difficult is it to replace in the field?
How about transporting your porta-potties around town? How many will fit on the back of a truck? Do the sides “give” so you can securely tie them down?
How long has the manufacturer been in business? If you need some replacement parts and the manufacturer is out of business, you are SOL.