I'm thinking Visio, LendingOne, FOAC, Ridge Lending Specialty products (I use Ridge) and similar.

I’ve watched the value of my first purchase increase by 20% (some say it’s more than that) and it got me thinking - can I do something similar again?

Appreciation may be similar, it’s hard to say, but you can get a pretty nice, large  house with amenities for $2-3 mil there.

The instruction sheet will tell you which models can be interconnected, and you can often get that sheet as a PDF from the manufacturer's web site before you buy.I've also seen a suggestion to make sure that wired smoke alarms are powered from a circuit that also has a light on it that is used relatively often - like the light over the stairs, or the front porch light, or similar. 

We used a similar strategy when we got started, to flip some of the deals where the numbers didn’t make sense as rentals, and fix-to-rent the houses that cash flowed.  

"garbage in, garbage out"I posted this link (HERE) in a very similar post here on BP which may be very helpful: https://www.biggerpockets.com/forums/44/topics/544460-price-per-sq-ft-for-new-construction-in-the-sf-bay-area?

I submitted one of my properties to a company similar to that called Opendoor dot com.

I got one by looking around and seeing as many similar houses as possible in the neighbourhood. 

Investors who follow a similar path to this example, what's missing in this picture?

You could have two properties that are similar and one could have 15% qualifying assets and the other could have 25%.A/C and furnace would generally not qualify for bonus depreciation, but on a nonresidential commercial property they now qualify for section 179.