this simply says that the IRS will not challenge your investment intent in which you rent the property for at least 2 weeks a year in multiple years and your personal use is restricted to the the greater of 2 weeks a year, or 10% of the number of days it is actually rented, And this doesn't count days you stay in the property while you are working on it.There is no statutory required amount of use or residency.

Challenges?

Proving they clogged the drain will be challenging unless your plumber has clear evidence (e.g. pulled wet wipes out of the line). as for their damage, if you require them to have renters insurance that should be available to cover the damage. lastly, code is something that is different from one municipality to another and may things can be not up to code but grandfathered in (e.g. aluminum wiring that was common in the 60s and now is not up to code) 

Is the challenge with scale that it's hard to keep tabs on everything?

Challenges?

Challenges?

Challenges?

Challenges?

Challenges?

Challenges?