But reality has a lot of variables all along the way that you are trying to estimate all up front.

In my limited experience(100+ lease ups) I would say that around 600 and lower you will start see multiple negative variables that usually overlap with my other non-score specific red flags.red flags=instant rejection=previous eviction or unlawful detainer, felony conviction, vehicle repossession, bankruptcy, foreclosure, multiple collections items...if it's BK or foreclosure or multiple collections, they can be overlooked with a maximum legal deposit(2months in ca) if they have solid income verificationWith C property you may have tenants with 400-500 score, because they have no credit history, or limited history with $50 unpaid phone bill or unpaid ER visit, they don't even know about because of moving around or just living check to check, BUT, they are a mechanic, heavy equipment operator, retail manager for 4 years at the same business that has been there for 50 years....

The tear down and rebuild will be roughly 450-500kI have a 3 yr old HELOC from my primary residence  and have 160k available with a variable interest rate.

I think I value having my hands on the deals and having a higher level of security, knowing that most variables have been accounted for by myself. 

I know there are a ton of variables here but just wanted to pose the question to get some opinions on what others have done.

I know there are a ton of other variables I could get into, but just spelling out some generalities.What have others had success doing in the area?

Quote from @Carlos Ptriawan: .... where I predict my home would be sold between 935K to 970K based on variability of comps and following M2 growth LOL .

I'm thinking about buying something, but I need to take into account all of the variables.

There are a lot of variables that can change that though.

There are many, many variables that influence timing of the work and which may end up costing more money.