If you want to build out a portfolio of multi-family rentals that cash flow to the point of not having a W2, that's one thing. 

(Of course, there is a factor that higher rating will increase my booking but that is not just coming from adding one or two amenities) Besides item 5 and 6, I am not sure how much other items will attract more guests to my business.

ARV is a very important factor here. 600 FICO is minimum. 

You need to build your credit.

How can any turn key advocating buy and HOLD not factor this in? 

As for building trust with sellers, communication is key.

If you want to build your portfolio and its a property that is already making money, why would you want to sell it?

You can build the tool yourself but it will take time. 

If your goal is passive income, it's not going to be in New Jersey when you factor in cost to purchase, management costs, and rent to price ratio, but what you can get is steady appreciation.

Unless it is a new build, and it comes with purchase warranties are an extra cost and may or may not even be executed when needed depending on the circumstances.