MEP, Hard to decide on a free standing unit. The most successful ones I have seen are part of the building. There are also some modular setups that are already to go. All you need is to run power, water and sewer but I have not seen one in operation. I have no doubt that in some situations a pet wash would be an asset but not in others. The ones I have seen that are successful are usually around other businesses like a small mall or a cluster of several retail stores. In an area where you are pretty much isolated I would guess would make it less likely to succeed. In either case, as part of regular daily maintenance program I don't think it would add that much work depending on the set up.