I have a flip in Louisville KY that we are a few weeks out from putting it on the market, but the past owner has an overdue account balance on his water bill for $300.

So yes, typically you will need all plans signed off on by a P.E.The third common component is a study showing that the additional fill placed in the flood zone by your planned building will not significantly decrease the water holding volume of the floodplain (in addition with other permitted or built fills in the same basin).

I don't know if I would go to that extreme, I would want my guests to at least have some running water and a bathroom.

I've got a ton of folks who can pour my foundation, but I'm looking for trustworthy, independent tradespeople that could pull my water, sewer, gas, and electricity out to this soon-to-be existing slab.I wonder how you all find these folks?

You might run into adequate HVAC capacity and needing to run additional ductwork (then determining a pro-rata billing set up perhaps) or even an additional unit with separate water meter just the same. 

Breakdown of the park:47 lots (6 rentals 15 owner occupied)21 filled17 vacant trailers (I have a crew that remodels trailers)9 vacant lotsLot rents: $298City water & septic - billed back to tenants. 

With mountains, water, and an outdoor community, it draws a vacation population.

The other concern would be if you pay utilities, this will increase water and electric bills.

Utilities you'll call and put in your name and water bill will stay with the property (at least here in Metro Detroit) but sellers will put some money with title in escrow in case they don't get a final water reading or pay that water bill before leaving. 

Case in point, we've provided a lot of parameters for our wholesalers and yet they still continue to bring us "great deals" that are not in our wheelhouse (i.e. mobile homes, properties not on City sewer and water).