The main house is a 4+2, and the back cottage is a 1+1, no shared walls.

Bottom line this once "cottage industry" is fast becoming a "major growth industry" very similar to the remodeling and fix and flip trends we saw in the post '08 meltdown. 

I have a cottage home I recently purchased.

All Boston has more vacancies than swiss cheese has holes.   

We have some other concepts,  Building cottages on small lots and renting/sale same!

Put a nice little ruffle in front of where the dishwasher is supposed to be, adds a little shabby chic/ cottage look and can be extra storage space for tenants.

@Jordan Alequin I have found that a SFH with a suite or a separate unit (cottage, walkout basement, garage conversion) can be a better ROI than a duplex.

Personally my plan when I eventually retire is to liquidate everything, home, income properties, everything except my cottage, and move into either a rental or a retirement home.

Convert a garage, walkout basement, cottage on the back.

This can be a good way to generate a larger income and build equity in a single property.House and cottage: Purchase a property with a separate cottage or guest house and rent out the cottage while living in the main house.