He complains for a while about my markup and we joke back and forth, but we end up agreeing on $25K if I will pay for roofing materials and he can have a couple months to close.

This is very clean looking and the material you guys provide is priceless!

There have been 3 occasions where the verbal offers materialized into a property visit and I have made 3 written offers none of which have been accepted.I have done all of this since October 1st, 2014.

And you may not have the money to pay them.From the lenders perspective they don't want to give you money until it is locked into the property via labor and material.

You can ask for larger security deposits, rehab the units with tougher materials, and make sure the parents co-sign the leases.

A violation of this paragraph shall be a material violation of this Agreement.8.

If it's noticed BEFORE closing the buyer should have demanded they will not close until the seller replaces it.You would have had to replace unless they were buying as-is.There is usually a provision int he purchase and sale that says the property will not be materially different from the time you went under contract or the buyer has the right to terminate the agreement and retain all the earnest money.If it happened after the closing then the buyer would most likely file a claim to have it replaced.If you were standing to make a decent amount of money off of this I would just replace it for the buyer and file a claim with your insurance.Otherwise there could be an argument over WHEN it was stolen (before they signed the papers or after)and they might try to sue to get money.No legal advice.

Do they know how to select the right materials?

Select final design and materials for the rehab.

I had a contractor put in a washer dryer down there about two months ago, and it connects to the shower, but everytime the washer runs, it discharges this sand/buildup material.