This is a common issue, but having stricter cost control measures or a contingency buffer in place could help on future projects.

There are clearly downsides - the investments are even less liquid than active real estate, they are completely out of your control and they are long term in nature.  

Nice area of the city but the buyer will likely be inheriting rent controlled tenants.

Many people tend to think that the Federal Funds rate controls interest rates. 

Two codes of specialized paint for order control, not the regular Home Depot paint, were necessary.

Ultimately YOU need to be the one in control so YOU need to understand what's going on more and you need your agent to assist you with that.

Maybe as a construction manager, warranty guy, quality control or something. 

Also it would be interesting to control for attributes such as 1) condo vs. fee simple and 2) modest vs. midrange vs. high priced homes.

At the early stages, the more control you have over your real estate, the better returns thus I recommend investing locally to make your dollar go that much farther and gain a good familarity with real estate before exploring out of state investing.

Specifically regarding plumbing you could add (depending on your State or Local Laws) "... 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..."