It sounds as if the owner is looking for an optimist to purchase this home. We know from the statement that the current system does not work. If it did, it would be useable now. So, as it stands, the mobile home is uninhabitable. Now the existing septic MAY be useable with updating but then again it's more likely that it MAY NOT. In order to figure that out you would need to have an expert come out, evaluate the system and the property and tell you some potential solutions. Sometimes there are no good solutions and the only option would be to have a holding tank that must be pumped out by a septic company periodically. That gets expensive over time. Replacement of a system is expensive all at once, up to $30,000 in our area. If this were something other than a mobile home we might encourage our client to look into it further if the price was right and the deal was contingent upon buyers approval of a qualified system. But mobile homes do not have the same potential for appreciation that another home would. Unless this home is in incredible, up-to-date condition (doubtful in our mind) and you can get it for just slightly more than the cost of land we would suggest looking elsewhere.