I recently found out about the STR rule that allows non-full time real estate professionals to do a cost segregation study and bonus depreciate part of the home's value and take these losses against their w2. I also found out that you only need 10% down for a second home loan. The specific requirements for these are interesting and I'd like some input from those with experience.

So my understanding is that in order for a STR's losses to be considered active (and therefore deductible against a W2), among other requirements, the owner must use that property for 14 days or less (let's assume <140 days total rented for simplicity). And for a second home, the owner must use that home for at least 14 days in order for it to not be a rental property. Is my understanding correct that if one was to purchase a second home that they put as a short term rental, they would have to use it for exactly 14 days for it to count as both a STR and as a second home? How strict is the IRS with these numbers? Thanks.