(I have tried AirDNA's free version and have gotten a rough estimate on revenue) Or any other ways to get a solid idea of the potential of the property to show to our potential investors?

You're essentially partnering with the seller/owner in this scenario.

To me the value in diversification is that it helps nudge you to look for other opportunities and revenue streams where you might otherwise just be content to stay in your lane and then you'd never find anything new. 

If I read this correctly, this essentially changes the 2 of 5 rule to 2 of last 10?  

but careful planning and documentation are essential""...making sure that your wife understands what she needs to do to document her hours and activities."

However they are missing out on all the revenue a property can generate.

It’s essentially the wealth you’ve built through homeownership.

Finally the pro formas that they provide are absurdly basic and neglect at least 25% expenses, so are essentially useless. 

Something has to get better in that market as the regulations are too confining and essentially up to interpretation by the city explore you engage with.

If you want some revenue numbers for similar properties to the ones you're looking at or anything to use in underwriting feel free to reach out.