This would allow me to raise the rent for the main house a bit over market but I'm concerned usage could get out of control and making my cashflow take an unpredictable hit.Does anyone see other options here that may work better than the two above?

If you are concerned about your sales income stability moving forward, just make sure your reserves stay big enough to let you sleep at night.

As I am not a spring chicken with my age..there are always concerns about "What happens if I die?"...

You are NOT paying for our labor and materials , its much more than that , office staff , trucks , tools , insurance , taxes , benefits , health insurance , etc are all part of the price .

As for foundation or other concerns about the condition of the property, there's no real way to know for sure since you don't have access to inspect the house before the auction (hence the risk).

We have a note in property stating for guests to contact us within first 24 hours should there be any concerns.

Since the potential properties can be removed from the list in last min,  my major concern is when i fly in, the properties i'd liketo bid on could be already invalid from the list at auction. 

However, landlords are investing heavily in upgrading office spaces to meet modern tenant demands, such as flexible work setups and health-conscious designs.

With solid records and compliance, there’s little reason to be overly concerned about the size of the return.

From what I remember, they addressed all concerns such as insulation, insuring them, or anything else that might come up without relative problems.