The photo on the right is a STANDARD PIER JACK and does not provide nearly as much vertical resistance and almost no horizontal wind or seismic resistance.

Does anyone have a "standard percentage or rule" they use for setting aside cash for the unexpected during a flip? 

This does not include accrued interest,mpreservation, property taxes paid, force placed insurance, etc.

Remember, these "wholesalers" are not licensed, not held to any standard, are usually out for a quick buck, and doubtfully have any E&O insurance.

You were missing Principal and Interest from your mortgage and also Management expenses.Based off of that I put your numbers into it.Rental Income             $2375ExpensesManagement               $190 (8%)Insurance                     $125Capital Expenditures   $71.25 (3%)Taxes                           $325Repairs                        $237.50 (10%)Interest                         $412.50 ($110k @ 4.5%/30 yr)Principal                       $144.85 ($110k @ 4.5%/30 yr)Vacancy                       $118.75 (5%)Electricity                     $250Water ad Serwer          $50Total                             $1924.85Cashflow                      $450.15Looks like pretty good cash flow from that.

I plan to pick up one property a year after that so that by 2026 I could leave my current job wihtout altering my standard of living. 

Right after you close on an improved property get an insurance policy that will protect you if there is a loss on that property.Do not cut any corners to make something look better.  

My main goal is to become a buy & hold investor, to start accumulating properties slowly and surely (in a pace of 1-2 doors every 1-2 years) until I have enough passive income to live my life by my own standards.

The design for your business card is unimportant compared to other things -- just use a standard template and then focus your time on the important stuff, like finding deals.

However the math is simple… run an amortization calculator see what the taxes & Mort payment are, and then know what a flat in that area rents for, With that said here is 2 typical examples of Albany propertiesNew Scotland area 2 family’s run around 220k, 6k taxes, 1k insurance payment would be around 1570 a month, typical rentals would be around 1300Washington ave areas 2 family will run around 140, 3500 in taxes, 1k insurance would be about 1000 a month, with rentals being around 1000 a month.So you pretty much can break even in the not as good areas, grab a roommate or 2 and you’re really cash flowing.But don’t forget about the big savings of the low down payment and locked in low interest rate when you plan on exiting in 2-3 years