We manage a portfolio of rentals across 6 states and are looking for the best way to track accounting, run investment return reports, replace quickbooks ourselves.

Each shipment will have a specialized shipment number, by which you can track the location of your mail package in the United States.

I've been using Stessa App to track my expenses for a couple of years now.

Background checks help verify the integrity and track record of the sponsor.

You are 100% on the right track. 2-1 buydowns are attractive options offered by sellers/builders to help improve monthly affordability but in all reality you aren't saving anything. 

Does anyone have any recommendations, or even better any spreadsheets, excel or web-based, they use to keep track of all construction expenses for Flip/BRRRR properties? 

Getting in the trenches not only is the best way to learn, but you'll be on the fast track to make the connections you need (contractors/vendors).  

Look for reviews and a track record of closing. 

Collecting rents is super easy and the bookkeeping features allow me to track all revenue & expenses for each property in a manner that makes filing my taxes at the end of year very easy. 

LTR are about 40minutes a month each for the same tracking.