For example, avoid wasting time comparing new construction with sun-soaked windows to basement units with stained drop ceilings.

A full gut and roof HVAC windows etc for 100k seems very low.

* The offices don't have windows as the building has adjacent structures.

But letting minor issues slide was my biggest mistake.

You will need to make sure that are no gaps in windows, doors, etc and that the HVAC system is well maintained as a tenant could argue that lack of remediation is the culprit for a high utility bill.

You need 6" clear from ground to bottom plate, and ground must slope away from house...5) Any place that water can enter the house (doors and windows, skylights, where roof meets eaves, etc...) should be checked thoroughly, if it's not raining on inspection day, you have to be really careful with this...any suspect areas, put a hose on them....

windows? 

Roof lines, window styles, and masonry/siding all play into this natural flow, and the biggest mistake you can make when designing your flips is not following the flow that is already present!

I did have to replace windows.

@Joseph LeibovitchYou just missed the window...Just before the FED provided their first rate cut, DSCR loans were down to nearly under 6% with 1 year PPP at par pricing.