Obviously you would want to subtract your assignment fee as well.

I typically subtract 3%, of the ARV.Realtor Fees: What is the commission you are willing to pay your listing agent (unless you are the listing agent) and the buyer's agent.

I'd assume it isn't until you can prove otherwise.Did you run a rental survey, subtract all expenses from potential income and get a NOI?

You can Google the name of the county and "tax rate" then multiply that by the new purchase price.Subtract expenses from income to get the Net Operating Income.Divide that number by the purchase price to get your cap rate (ROI without debt service).If you're going to have debt service then subtract the annual debt service form the NOI.

An appraiser would not just take PGI (potential gross income) and then subtract an "as is" vacancy to negate any value of the excess land. 

Subtract rehab ($35k), front end closing costs ($1,500), taxes/HOA/utilities for 4 months ($3,500), and back end closing costs (6% * ARV + $2k misc = $20k).That leaves $240,000 for purchase price + profit. 

Subtract financing expenses (principle and interest) from net operating income to get cash flow. 

My intentions would be to assign the contract so i know i need to shoot for the 70% rule, minus the cost of repairs and subtract the amount i would like to make, but how do i get a good accurate base value for the home, the number I should work off off?

Step 3: Calculate the total amount of cash you’ll need to bring to closing by subtracting the total loan amount (i.e. your total from Step 1) from the total costs (i.e. your total from Step 2).

Don't forget to subtract any immediate needed repairs from the calculated value.