Also, I would prefer to have a renter cover expenses during the cold months and make sure there are no issues with pipes freezing. 

The motivation is not based on assumed guilt as opposed to simply covering all their bases.Do not panic, proceed with caution.

Also, making sure you home owner's insurance is setup to cover the rental onsite and having adequate coverage will take you a long way.

Even if it was concerete, he should have made sure all pipes were covered adequately from any concrtete falling into the pipes.

Tenant screening is also a very big factor.

I'm only nearly 5 mos in on my venture but we need to carry the following for our residential care (assisted living)  licensed for 41 beds - but we can hold 36 beds in our current configurationGeneral Liability (We buy through an independent broker - basically covers medical malpractice, any slip/falls etc)Workers CompAnd even though you arent interested - Non owned auto insurance in case staff use their own vehicles to run an errand etc, building insurance for wind/hail etc inc general property liabilityAll of this runs around $33k to 36k a year for us - thats before health insurance for us etc - Work Comp is the most expensive part of that mix.Your best bet is likely not to find the coverage by calling yourself - you'll just waste your time - find a broker that can sell you this insurance - as far as limits - some of the limits are state mandated and will be in the regulations. 

Umbrella insurance will cover up to certain amount, like mentioned in the other article I find it hard (for myself) to see how I'd be sued for something in excess of the appropriate insurance coverage.

If a lender has $500k to lend to you, they have $500 to cover their processing fees and an appraisal.I'd be careful...

I have had this happen twice in 5 years.The biggest issues that are more common with poor PM's are bad tenant screening and lack of inspections.  

Tons of info on BP about screening tenants....even if you hire a PM, you should be well versed in how to do it.