This is the magic formula.

There is no magic formula that can fit any and all investors.My advice is start with one or two (houses, condos or 1-4 units building) see how it goes, how you like it.

Sometimes in OC ARV formulas go out the window and investors will pay way more than you think.

@Kevin Keene , Here are my thoughts:First off, you should definitely NOT be relying at all on Zestimate for values.Secondly, it took me a bit to figure out what you were doing with the ARV calculator formula.  

Success is not a straight line formula.

@Kirk Rohani,If you plan on rehabbing and selling it, here is the formula that most rehabbers use:ARV minus 30%, minus the repairs, equals the max price you should pay.$240K minus 30% = $168K, minus $35K repairs = $133K.Because you plan on not using a Realtor to sell the house, you can add 5-6% to your purchase price. $240K minus 24% equals $182K, minus $35K repairs, equals $147KAs a rental Property that rents for $1500 per month, the final price should not be more than $150K.Some landlords are happy with 1% of the purchase price, and others won't settle for less than 2% of the purchase price, for the Monthly rent.Raymond

As Joe said, in certain markets you can get property for a song.

There is not formula to produce an accurate figure because it all depends on revenue and expense correct?

Without seeing how your formulas are calculated, I can't tell you where you're going wrong. 

Most will say 'no' but just keep at it.The basic offer formula is 70% ARV (after repair value) minus repairs minus your fee.