I would be concerned if you see evidence of mold, mice, termites or a severe lack of cleanliness as these can damage a structure over the long term.

There is water damage in the basement NOT under the plumbing, so I'm guessing its the radiant heat. 

The tenants generally don't damage the houses, but the economy outside of downtown Detroit is still rough and people may stop paying and you have to start again. 4.  

A couple of months ago a storm came through and damaged a roof on one of my houses, we got the roof fixed immediately but it had caused a portion of the ceiling in the living room to cave in.  

. $500 (rounding high for easy figure, based on GFE from bank a little bit lower)HOA- $340/month, just updated by HOAInsurance- $271/year or $22/monthRent- $950/month$500+$340+22=$862/month in total costs, so $1,000-$862= $94/month cash flowMy thinking could be nieve, but I just believe that I will never have to pay for new roof, damage to the property (outside), lawn care, pool maitenance, etc.

Occasionally a tenant has done some significant damage, but so far nothing that was insurmountable.We put an emphasis on offering good rental units (B & C), maintaining them well, establishing keen rental criteria, thorough tenant screening, a strong rental agreement, clearly discussing every aspect of the rental agreement with the tenant before we hand over the keys, establishing and maintaining good relationships with tenants, good relationships with neighbors who will alert us as needed, a good relationship with local law enforcement, regular property inspections, swift follow-up to rental agreement violations, sufficient insurance and a sufficient reserve fund.We stand behind our mission statement:   "We strive to provide safe, clean, affordable, comfortable, and quiet housing for responsible renters in the neighborhoods of West Vancouver."

For years the insurance industry have used firefighters to "bird-dog" properties that are damaged by fire.

The only information I am getting is from the EzLandlordForms website that says:"California Civil Code requires the landlord to mitigate damages if a tenant needs to break a lease early.

Also, as @Marcia Maynard  mentioned the damage could easily end up being more than that if the tenant leaves in November.

About 18 months ago, I looked at a townhouse that was selling for $85,000 and needed probably $40-$50 of rehab including fixing the water damage.