Building an RV Park from scratch under 50k?

I suspect if the "RV Park" is in the Recharge Zone of the Edwards Aquifer that a conventional septic system cannot be put in and a treatment plant must be installed. These treatment plants cost about $6,000 to $8,000 per home in normal soil, so for a large installation I would guess that you're talking about costs in the $15,000 to $20,000 range for this project besides using probably several acres for spray fields. I doubt that any licensed installer would touch such a project without proper permits from the appropriate regulatory agency since such unlicensed installations could be very expensive in fines or even prison time.