Here's my primary reasons:Expenses disproportionately impact lower rent collecting properties For illustration purposes compare two identically designed 1+1 duplexes in the same market.  

Adding rooms does create the potential for more conflict but carefully thought-out floorplans, designate wet and dry storage spaces, and provide supplies.

A HELOC or loan on your primary could provide funding, but that is typically not designed for longer term funding - i.e. a down payment on a multifamily....

I understand home designs are pretty expensive, and cannot just be applied to any lot/existing neighborhood.

It is more of an accounting platform designed for real estate than a management platform.For my STR company I use hospitable and clearing.co for my management and accounting platforms.

Some had other events in other states designed to elicit high emotions and fun, solidifying what was basic information as something secretive, which it really wasn't, it was just more enjoyable and easier to learn in the 'fun zone'.

After 8 years as a director in the kitchen and bath retail space, I'm bringing my positive energy and relationship building to a wholesaling firm covering Los Angeles and San Diego counties (we specialize in single family homes priced between $400-$1.7M).

@Joshua Thompson already linked the long post that I wrote to answer your question:https://www.biggerpockets.com/forums/51/topics/1215989-expla...Based on your subsequent comments, you missed the point of my post: it DOES NOT matter whether your accountant holds a CPA or an EA designation (or neither of those two).

SPC is great for moisture-prone areas like kitchens and baths, while WPC is softer underfoot and ideal for main living areas.

Maybe find a good designer that can provide services to install and setup the spaces.A lot of these ideas are going to depend on where you are buying.