If I have this supplemental income I won't have to work anymore, barring no unforeseen rent decreases due to economic crashes. 

Dealing with tenants, unforeseen expenses, construction/rehab costs, etc.

In my opinion you’ll always have unforeseen repair expense but if deals have solid cash flow and equity then you’ll be fine.

Remember once you buy something, you may have to inject money for unforeseen events.

As you mentioned, having those reserves during the flip for unforeseen repairs can be crucial to the 1st flip.

Cost overruns, delays, unforeseen issues, market correction...they are all possible. 

Generally speaking, the newer you are to investing, the more cushion you'll want to build in for mistakes and unforeseen circumstances.

I am going to start flipping properties as my primary income and I need to build a business plan.My target market is the Myrtle Beach, SC area.Any feedback on your preferred hard money lenders, unforeseen pitfalls in the process, typical days from purchase close to the close of the sale after rehab would be greatly appreciated.

Be sure to also set aside part of your cash flow for unforeseen expenses (vacancy, damage, repairs, etc.).

Even the best ones can run into an unforeseen issue and have a disaster.