You don't go to a tax attorney and ask them questions about traffic tickets.  

The same people get mad when the price of Newport’s ,booze , dog food for their pit bull and lotto tickets inch up but they still buy all that junk anyway .

Sure, they may hit the mother-load once or twice, but eventually, they'll buy another lottery ticket because they've squandered their resources. 

When the big ticket items where last updated/replaced: hvac, roof, etc. 

I would keep capex at 10% as those are long term savings for big ticket items but since you just rehabbed you can keep repairs at 3%.Looks like it should do pretty well for you once you change the capex.

If an amateur Real Estate Investor doesn't have enough cash to purchase a property, and instead chooses to tap into their 401k for the down payment, what are they going to do when the big-ticket repairs unexpectedly appear, I.e. new roof, new heat system, going a few months with vacancies while the mortgage, taxes and utilities still need to be paid?

Chase ink bold. 60k rewards points, that's enough for a round trip first class ticket to Europe 

I'll take a ticket!

The save and use compound interest model could take a life time and you may only reach a fraction of the 100M net worth figure or you need luck like others have mentioned.The quickest way is to do what the rich do and that is to do what JJ Marco focuses on in his book the Millionaire fastlane by either focusing on the 1) Magnitude or the 2) speed/velocity.Increasing Magnitude would be like increasing the ticket item size so if you're a real estate agent instead of selling 250k homes you sell luxury items that you receive your 2.5% commission off of 10,000,000 instead.Increasing Speed/velocity would be how many times you can transact and earn that commission above, profit above in whatever business model it is  whether you're a RE agent, you're selling burgers, or widgets. 

The tickets went to the property.