The linked article discusses the following:
- Home office remodel
- Backup power generator
- Sunroom addition
- Upscale master suite addition
- Bathroom addition
- Upscale garage addition
Don't personalize your rental properties either. If doing upgrades at all, go with generic upgrades when doing maintenance. That includes the color of paints, carpets, and drapes or blinds. Your objective is to appeal to the widest market, the widest range of tastes, within the property's and neighborhood's price or rent range.