The 3rd thing that has reshaped my entire opinion of the tax advantages of real estate, is seeing my 88 grandfather holding five quite valuable illiquid properties, long story short it’s a mess, it’s causing family drama, he is in zero shape physically or mentally to manage them, the all have cap-ex needs, again these were amazing buy’s literally multiple properties he bought for under 50k that are now worth over a million but there is probably a time and a place for owning real estate, so I don’t really have a need to own more than maybe a few properties into retirement.

However, these activities should not cause concern for them.

A contract developed 10 years ago might be outdated in ways that will cause you an issue.

Have the agent video everything, just in case tenant is there and causes a scene or refuses access.You will either get the work done or have a video supporting your eviction.

We just discovered a crack in the concrete slab foundation that is a borderline major problem:- It is a vertical crack about 1/8 inch wide that is at least 9ft long, which is causing a 3/4 inch drop in the flooring and some evidence of old (luckily) limited moisture and termite intrusion. - BUT, it also appears old and probably a symptom of the original house settling.

I imagine it's higher than a typical single family rental considering it looks like the host usually ends up paying for any damage caused by tenants due to a variety of reasons (tenant refuses to pay, damage happened in a common area and it's not clear what tenant caused it, etc.).- Rental loss - PadSplit claims they collect 97% of rents, but I've spoken to a few hosts who have said that a much larger % of their tenants get kicked out owing $500 or more in back rent that is rarely ever collected - what's your experience been here?

For me personally, I would not take on a mortgage if it was going to cause the property to be cash flow negative.

If forced to cure - and it will be a condition of remedy - the tenant can take action against you for damages from leasing an illegal property. 

Also,  make sure your turn over costs account for the smoke damage.

And you avoid things like damaged properties (guest insurance from airbnb or prop manager themselves cover that), evictions, collections, etc.