Everyone told me to just get the perc test done and I'd know if I could build. So I did, it passed, and I bought the land feeling confident. What nobody explained was that passing a perc test and getting a septic permit issued are two completely different hurdles in Texas Hill Country counties. My county had updated their setback requirements from property lines, wells, and drainage features between when comparable parcels were permitted and when I applied. My 12 acres suddenly had almost no compliant footprint for a conventional system. I had to go engineered aerobic, which added about $14,000 to my build costs before I'd poured a single footing.
A passed perc test is a necessary condition, not a sufficient one. You need to sit down with your actual county environmental health office — not a third-party inspector, not your realtor — and map out exactly where a permitted system could physically go before you close.
Anyone else find that county-level permitting changed the game more than the land itself? I'd love to hear how this plays out in other regions.