For long term rentals, look at vacancy rates, rental rates and expenses.

Like you I didn’t budget rent increases in the 7 year and only $100/mo increase in the 5 + 5 but what I wanted and got was 1) no vacancies for 10 years and no turn over costs.

I feel that this is a great risk because i would no longer have personal funds to cover any operational property expenses /vacancy / PM fees for tenant searches,etc.

Retail properties take a lot of cash to operate and a vacancy could crush you especially if it's caused by a general economic downturn.

Recognize filling your vacancies as a major aspect of your REI business success and deal with it quickly and efficiently every time.Do your best to find quality tenants.

You are going to have lots of vacancy for foreseeable future.

On that ~3622.72 you can assume 30% to vacancy/capex/management so you will end up with a ~2535.90 profit each month, or a ~30,430 cash in your pocket a year at 30 years owning this property before any applicable taxes. 

So, if the house is in great shape, is in a "B" or better neighborhood, you have great PM, and the numbers work so you cash flow okay after reserves for vacancy and maintenance , then I would buy it.

I've looked at his utility/mortgage bills and estimate that getting $1800/mo would cover all my brother's current expenses, plus setting aside 10% of his expenses for vacancy, 5% of his expenses for capital expenses, and 10% of his expenses for repairs & maintenance.

It can't hurt to have more than you need when a serious problem arises with your property but, it Can hurt if you don't have enough money stashed.I would have at least 4-6months of rent for vacancy saved for each unit, and 3-6months of rent for renovations/repairs saved for each unit.