My longest recent rehab was 2.25 months and added a half bathroom, took down 4 walks including load bearing, put up 3 walls, new plumbing, electrical, flooring, huge percentage of drywall, an eye brow porch, new kitchen with full layout change and new bathroom with full layout change.  

The layouts are easier to work with and manipulate to make the space feel as modern as possible. 

Advice on Layout/Design: For those who have added ADUs, do you recommend standalone units, garage conversions, or a combination of both?

Views, location to attractions and layout of property can make or break you in a good location or not so great location.

Quote from @Mary Jo Carruthers: I have seen houses where folks did it anyways without the permit but that is really value destroying as it will make it very unlikely to sell for top dollar with that layout. 

There are many options, so instead of me listing a million things, it would be more helpful if you could lay out a few options you're considering, and I can provide some feedback from there.

I made the layout more user friendly, added a whole wall of closets in the main bedroom, totally gutted kitchen and bath.

For the 4 plex you are spending an extra 80k in renovations (I question your 110k renovation number to get to 4 units - this could be low but I don't know the square footage or layout).

These can sometimes offer better cash flow, especially if you’re in a family-friendly area with unique features like extra square footage, an ADU, or flexible layouts.

Curious as to what the layout you chose and how the building experience and whether it was worth it!