I am a licensed builder and have replaced hundreds of roofs and I would never even consider being responsible for ordering all of the materials that are needed.  

If I die unexpectedly, my family is taken care of.Retirement accounts were meant to replace company pensions by reducing employee income during employee working years to save businesses money.

Think a big component is amount of available rooms where people could sleep.

Leave for tenants- If I leave for tenants I would note it in the lease that these are the tenants responsibility and once broken I will not be responsible for fixing and/or replacing.

You might give some contractors a call and ask a general questions such as "What is the average cost to replace a two story house roof in XXX area?"

We are having constant a/c unit replacements in my 15 unit multifamily . 

However, we've explored using some corrugated metal fencing for the next ones we need to replace, something like this.

Funny thing is if you’re only looking to get a mortgage for the purchase price (minus required downpayment) it’s usually required to be under 6 months for a cash sale replacement loan. 

Replaced a few light fixtures is all!

@Anna Bee Interest rates are simply one component of a real estate transaction.