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).  

But they typically abscond with the rest, squandering it on personal expenses or high-flying life styles.COMMENT: This is common for any type of fraud.They may also use some of the proceeds to support an elaborate "Ponzi" scheme in which money coming in from the sale of new notes pays the interest on older notes.

Does anyone make buyers sign a hold harmless similar to buying a bank home as is or is that not common for flips?

It can vary WIDELY between lenders some times with this type of lending.Some other common differences between the two loans:Appraisals – Conventional loans will always go off of “sold comparable properties” (or comps).

I would like to hear more about how common it is for stays longer than 30days in LA.

I agree stick to more common asset classes like build to rent and horizontal, 3 story walk up apartments, mixed use, commercial planned development, planned developments for residential, hotel / hospitality, single and multi tenant retail, office.