Abandoned Septic System

[Xi Chen]

Hi BP family. I am doing due diligence on a 6-unit property. According to the seller, a septic system was installed on the property a few years back, but soon after that the property was switched to public sewer. The septic system is offline but remains underground. Seller has no plan to take it out and told me the system was only used for 6 months and could even be sold for some money. What concerns me is the liability that comes with the septic system if it leaks or collapses. What should I do as far as the due diligence goes? Do I need to order a Phase-1 inspection? If it turns out to be in good shape, should I have it taken out? Thanks!