I don’t know how common vacancies are but I would say I could cover about 4-6 month in case of an emergency  

Usually a pattern will emerge on a 'normal' deal in your area.

I learned my lesson and am keeping reserves  for emergencies and lower LTV on financing.

Are there any emerging areas near Charleston, since it is getting so expensive?

There was no emergency shut off switch before but i asked the hvac contractor to install one and he did ( located inside the apt).

They tried to save money by filing themselves but ran into procedural issues that ultimately delayed the process by weeks.

Using a 401(k) loan reduces your emergency liquidity, which could make the investment riskier if unexpected costs arise.

Your $30k should be your emergency fund and not used for new investments at this time.Consider talking to a CPA or financial advisor.

They rarely have an over-leveraged emergency or catastrophe.Of course they will not grow as fast as the investor using leverage and NOT over-leveraging. 

The discipline to run on a budget for a number of years or decades depending on your math, doesn't factor in emergencies or market changes where the HELOC could be used to invest in other places.