Curious about lagoon systems

Im looking at a 21 space park with city water and a lagoon in Southern Illinois. Owner says its an aeration lagoon. Is this a deal to run from or with the proper due diligence and a backup plan in case the lagoon fails (not sure if there is a backup plan) would it be something to proceed with. It is at a 13 cap in its current condition on our verbally agreed upon price. Mainly older single wides, 80% being park owned which I would sell every time one comes vacant. What type of due diligence on the lagoon would you suggest if it were a deal to proceed with.