Then I found out even if it's approved, 2 families are built to different standard than 3's, like requiring fire escapes, sprinklers, and cement walls for furnace rooms.

Basically, something like a 2x4 or 2x6, between each pair of studs, with the broad side towards where the cement board/tile will go. 

Plus, none of them consider the popular multi-generational style living -that is the future. lolI love the style of modern cement homes like in Merida, Mexico for example and many other parts of the world.

Then he used metal studs to build a frame to attach cement board for tile and that part was a pita.

For many of the doctors, bankers, dentists, or other high-hourly-rate work that also has high time demands, it simply makes more sense to buy something stabilized and participate in the other benefits of real estate, namely debt paydown, cashflow, and property appreciation. 

.* Minimal landscaping and plenty of parking, more cement!

Once that water is trapped between the vinyl plank and the floor underneath, it's all over if cement is underneath, it'll eventually dry in 3 or 4 days but it just wasn't worth the constant risk of threatening lawsuits from tenants thinking they are sleeping in urine and feces.

I would call it a non-issue as long as you plan a siding over-lay and the property does not have any structural issues form the added weight of the chosen material, ie don't go cement board, think vinyl or engineered wood product. 

You can also seal the cracks with a cement product that has some flex agent in it, and stain the entire patio to blend it in.

Did you pour cement for the pads?