Building an RV Park from scratch under 50k?

They are lost. If they dont know for fact that it can legally be done they are wasting every dime. There could be next to no rules and there can be everything from setback from property lines to an expensive septic system. More and more often it seems that I hear people say that they can no longer install a traditional septic system. It's not comparing apples to apples but my sons above ground septic on an acre home site outside the city of Arvada Co was $28,000 and that's only sized for a 3 bedroom house. Septic are usually sized by bedrooms/number of people. When you mention flood plain it makes the possibility of a raised septic all the more likely.

By being the bearer of bad news you will end up hated. Believe it or not when I have been in similar situations I have even been blamed!!!!