In most places that setup is house hacking, not a separate ADU, unless the code allows a legal second dwelling with its own kitchen, parking, and zoning approval.

I would feature the kitchen or lounge.

So $50K on new HVAC won't be rewarded with higher rents as much as $50K on new kitchen, bathroom, flooring, windows, etc.

Kitchen remodels are harder to live there while they are happening. 

Kitchens – Still the king of ROI.

Most hotels dont have kitchens in the rooms , water heaters , rooms are small , electric isnt metered per unit .

The kitchen, dining room, and living room are all connected with a mostly open floor plan.

Thrift /FB marketplace for fun decor pieces that make your listing stand out, buy kitchen stuff and pillows and mattress protectors at Ross.

Remember 4 units with 4 tenants has virtually 4 times the maintenance/cap ex as a single unit due to 4 times as many kitchens, bathrooms, etc. in the absence of a local experienced LL examining your underwriting writing , you can use 50% expense/vacancy ratio which can provide a rough estimate of expenses/vacancy.  

So I don't spend any $ on a mower of any quality, I instead get new windows, a hot tub, update kitchen.