Then I organize them by the size/scope of the work they can do - e.g. full scale renovations w/ vertical/horizontal extensions, quick kitchen and bath renos, etc. 

My favorite was they replaced the horizontal soil stacks in the basement with PVC, but didn't support the original cast iron ones that still were in place vertically...

It doesn't *have* to go straight up from the basement to the roof - it can go up, turn and run horizontally for a while, then turn and go up again - but finding a space for it in an existing house can be a challenge.The 90% and up furnaces can be vented to the outside with PVC drain pipe. 

@Nate Barbee Slope angles are defined as above, with the first number being "x' in the horizontal direction" and the second number being "x' in vertical drop".  

This isolates each property horizontally within the umbrella of the one IRA.  

I just use Craigslist and a posterboard/calendar with 23 horizontal lines to manage my 23 STRs.But I guarantee you that my types of renters are completely different than yours. 

@Shane Melanson  Cash calls are not fun.. unless you state that there will be cash calls from time to time.In todays market we are doing the same  CASH for the dirt.. and only hang debt on horizontal and vertical.we are in the SFR space so a little different than your commercial deals we cant really pre sell legally . 

are you talking about a horizontal regime ?

Obviously there is the number of loans per person limitation but I didn't know if there is another strategy at play. our lines of credit are for value add short term deals and or horizontal development of a community and vertical construction..

You will still have the granularity by tracking each property horizontally instead of vertically.