Fraudsters know that your only hope is to incur expensive legal fees that will drain you of more money but have a very low chance of success; and therefore you won't want to incur throwing good money after bad to go after them. 

The opportunity arises after a family member, who has a clean title and owns the home outright, let the property go down the drain.

My dad broke up the concrete in just a few locations so water could seep through and drain into the soil, then filled the pool with the cheapest stone and clean soil locally available, then planted grass.

Hello, our rental home had a/c unit drains into the p trap in one of the bathroom and clogged the sink in upstairs.

Since you’ve offered the $300.00, honor it.Notify them that moving forward you will not be able to provide any further rent credits and offer to break the lease if they feel the living arrangements are no longer working for them.If you feel the above is something you are not comfortable with, I wish you the best of luck with tenants that’s will drain you while they occupy your premises. 

This time, I sent a plumber to unclog the drain, but he left without addressing the washer area.

However, the ell includes the neighbor's septic drain field.  

PermaSeal recommended a drain tile system which I agreed to.

Tenant also agrees to the following:-All drains, waste pipes, and plumbing are accepted as clear by Tenant at the time of occupancy, and any material blocking them after occupancy shall be repaired at Landlord’s cost, unless determined by repair person that such blockage occurred during the time Tenant controlled the Premises and due to some fault or negligence of Tenant, specifically excluding blockages caused by roots or backups from the street.

Make sure water drains away.