Isadore, the primary flaw in your idea is a common one among new investors.

She is currently locked into a lease, but she will be $900 short on rent this month and she says it is getting harder to pay every month.The rising cost of pretty much everything is straining budgets, especially of your working tenants.I see "it is getting harder to pay every month" becoming more common. 

It is the most common way to achieve the returns sought by the LPs.  

Used to be common in the past but not anymore.

No, this is common for states to not follow the federal guidelines when it comes to bonus depreciation, there is no exemption or other work-around.

This is common.

That looks like common surface mold due to lack of ventilation.

Is this a common phenomenon?

It is very common that they will subcontract out some of the more specialized work. 

Some common ones that come to mind in addition to a hot tub are a cedar sauna (gotta lean into that Minnesota sauna culture - check out Cedar and Stone out of Duluth for some really cool sauna ideas), snow shoes or cross country skis, or even just a nice outdoor firepit area with tons of firewood (you could also include complementary s'mores supplies for every reservation).