My wife not comfortable putting our house as equity, therefore we are utilizing other options to fund investment properties. 

Your income needs to be 100x it and you need to invest 10% of your net(so less than $5mil) annually in structured product type investing incl RE, let it season for 3-5 years, re-invest the first bit of profits and by year 8-10 you should be comfortable.$500k annual income is alot for your average folk, but it's not "retire me" income at all.

The easiest spot would probably be the dining room and change the office to more of a smaller dining area. 

Are you suggesting that being crammed in a small hotel room represents a better experience than being in a comfortable homey Airbnb?

In my experience, allowing these professionals to guide you can be highly beneficial, as they are likely to recommend properties they would be comfortable managing.

Personal Circumstances: Consider your comfort level with debt and risk.

The answer would be partially dependent on what are you looking to get out of it for rent and what type of risks are you comfortable with?

I'm not comfortable with them, especially for the first 4 items.Would you kindly explain to me for each of them?

Like most service industries, there is nothing more important than the human touch as that is what people relate to and feel comfortable with.

Are you looking for steady, low-risk passive income now, or are you comfortable taking on more leverage to scale faster?