Check if there are large trees growing around drain field area. If there is, be cautious. One of my rentals had flood due to drain issue. I finally changed to city sewage. Besides construciton and replumbing fee there is connection fee charged by city. It could cost a big. Some cities won't allow rebuild of septic tank if there is sewage connection available.
Once there is slow drain problem, it is a few hundred $ to pump. You can not wait for even one day. Could be stressful situation. I have done caustic treatment, pumped numerous time within one year before I decided enough is enough.
