@Louis Jara We had nearly the same thing here in PA, except it was two failed systems. It ran into a municipal wall and essentially required a full replacement of both. The only fix was an investor willing to take on a huge burden for a few months to tackle the project. Many lenders won't touch it, but private money or a JV where the lender gets ownership after the reno is worth exploring. I'd lock in a real septic bid before you finalize the capital stack. What's the as-is vs. repaired value looking like?
Lenders will look at it, but most want a known problem like a septic system fixed or funded before closing, so an as is sale with an open repair is a hard sell to a bank. The cleanest structure is a holdback, where part of the loan sits in escrow and pays for the septic, or seller financing with the septic cost taken off the price. Bridge or hard money works if you plan to fix it and refinance, but it costs more. For a small RV park, local banks and credit unions are usually the ones that will take it, since most lenders treat it as a specialty property.