From an engineering standpoint, in Texas, water and sanitary typically run on opposite sides of the street due to regulations on separation distance.

My recollection of the city's ordinances on sanitary conditions/occupancy is that they are otherwise based on occupant per square foot. 

Pipe type, size, grey water sanitary runoff (y/n), other plumbing issues, frequency of issue, etc. 

I believe If you can’t analyze it on a bar napkin in ten seconds then it’s probably a lousy deal .

Why would the rain have anything to do with your sanitary sewer backing up?

You could literally write a P&S on a greasy napkin and have an enforceable contract.You might consider getting a real estate attorney to help.

If you are you can have your lawn service report to you whether or not they feel that the yard is clean enough for them to do their job in in as sanitary a manner as possible.

On current income back of the napkin math puts you at under a 5%cap which is trash.

College Hill Properties, where the highest Massachusetts court held that renting to 4 or more students in one apartment unit of a two and three family home does not turn it into a“lodging house” requiring a special license under the Massachusetts lodging housing law, provided that the apartment meets all other sanitary and building code square footage occupancy thresholds.

Some of those variables are the size of the park, number of vacant spaces, number of POHs, number of vacant POHs, number of MH spaces, number of RV spaces, the park amenities, the age of the park, underground infrastructure age and condition, park location, size of the market, value of SFR in the market, water or well, sewer or septic, other utility sources and whether or not they are direct billed, deferred maintenance, cost of management, and more.However, there is a basic "back of the napkin" evaluation that will usually tell you if the deal is worth a closer look.