My words of advice are to use tiny nails on the end caps and some silicone underneath where the DW is.

Q1: if I put two tiny homes on wheels end to end with one wall being common, is that a duplex?

Even with a decent sized portfolio at 62 units I only need a tiny fraction of the population to be good people who want to rent my apartments. 

It's basically a tiny version of a central HVAC placed in various rooms. 

I think an irrevocable trust would only work if I were a family member (and could receive the property through an exclusionary transfer, which wouldn't trigger a reassessment) Yeah, the property could be worth more, although the lot is tiny....36 by 45 feet, and no onsite parking or even a yard to speak of.

(It will take another year or so before I can show a solid rental history on my first rental purchased last year; until then I won't qualify for another mortgage).I started construction on an accessory dwelling unit in my back yard, a carriage house (aka a large shed) that will become a not-so-tiny house.

(quantity over quality kinda thing) 5.

Chicago is so vast and diverse that 400k can get you a tiny condo in one neighborhood and a 12 unit in another. 

There are a lot of property managers (quantity) but not a lot of property managers who do a good job (quality).

My cheapest overall purchase price was $8,500-- but we had to re do everything and had to put about $15K into it, ARV is likely $75K, very cute but tiny house-- currently rented for $700/mo.My cheapest/best total investment, and honestly probably our luckiest one--  was a 2bd 1 bath-- $10,000 at an in person auction in 2017,  only had to put about $7K into it-- currently rented for $650, ARV is $100K.