That is entirely up to you, Mike, and a great question for your Buyer's Agent. Is the home already priced to accommodate replacing the septic, and has it failed? You should opt in for a full home inspection including well and septic - charges for these inspections vary by locale so check with your Realtor for several names of qualified inspectors. Currently, there are 4 homes in our market with similar issues - in 2 of them the home seller opted to offer escrow at closing for the septic replacement and in 2 the seller opted to lower the price to accommodate that replacement. Good luck with your house hunting!