Succeeding in food service industry is difficult at best, but than succeeding in multi-location food service industry, now were getting into a multiplier event of rarity in success, that sure as heck sounds like a unique area of advantage. 

My money is just sitting in a money market account gaining 4%-5% which isn't terrible but with a goal of eventually owning 10-15 rental properties what would be the smartest way to multiply my money for long term wealth? 

Add up all your bills monthly on your credit report- mortgage, taxes, insurance, auto loans, student loan balances X 1%, any other debts  and multiply that total X 12 = the amount of savings you need.IF you decide to get mortgages keep your income total to 36% of every single debt.

So the nature of a corporation is to multiply, than consume the market economy, and lastly to lay waste to the persons in such to charge ever more and spend ever less.

So, the answer to the question depends on the time period and location (and whether or not inflation adjusted prices from the past ten+ years will hold up long term).As you stated, the benefit of using leverage to multiply the impact of appreciation by 2-4x is not isolated to real estate but many of us consider that benefit inseparable from the benefit of real estate appreciation because of the readily available financing, the small initial investment needed, the passive nature, and the resulting high multiples (10-20x) of real estate...all compared to other direct owned businesses that are achievable for the average citizen. 

If you want to pretend a property will go up 3% in the coming year, multiply ARV (how do you figure ARV, the value of a property by the way?)

The IRS recognized this and made it easier to claim the home office deduction by multiplying $5 per sqft of office space.

So, can I multiply this rate by 2 since there were both my husband and I?

That said, I like to use a general ROT (rule-of thumb) that my units will be rented out 10 out of every 12 months to asses what I need in reserves (it's just much easier to calculate Revenue with multipliers of 10).  

This fraction shall then be multiplied bythe Consumer Price Index percentage increase for the previous twelve (12) monthperiod in order to determine the percentage of increased rental to which the landlordis entitled.