I'm thinking that this is a useful asset protection measure to leave the property encumbered.Is this reasonable tactic ? 

That is fine if it is the right size and material, but if not, why not measure it and go to the home improvement store and buy the material to do the repair right.It was taking them a longer than average time for them to rent the house and it had already been vacant a month before that due to my last property manager.

I think using a "return on equity" calculation every year is a good way to measure whether or not to continue holding a property. 

I believe Portland and other cities are considering similar measures wherein you must have very, very good reasons for not renewing a tenant.

We can measure the roof online and get specs. 

You swap them out on a fairly regular basis either as preventative measure when they are nearing the end of their life, or as a restorative measure when they break.  

There are some areas that do not allow certain types of rentals, or have more of a stringent process you must adhere to.

Larger buildings have fire alarms and sprinkler systems; fire walls; wider hallways and stairwells with double exits, etc ... all measures to increase the available window to exit a building in the event of a fire.

As Ashamann01 said local small banks may have construction loans and less stringent guidlens but cheaper than hard money.

The most reliable measure of Fair Market Value is....