So we are ramping up to make our next purchase hopefully in the next 6 months.My goal is to at least supplement my retirement with rental properties, but would love to be able to someday get into investing full time and stop working for the man.

In order to buy down the initial rate for the temporary payment, a lump sum is paid and held in an account used to supplement the borrower's monthly payment.

Usually, you continue to pay the preferred return until you sell, unless you have "debt investors", in which case, you will pay a fixed interest rate for a set number of years, and at the end of the term, you owe them all of their capital (which you do through a refinance, supplemental loan, or sell.).Acquisition fees and asset management fees are also typical.

Eventually, find value-add deals (even if you might need to supplement with HML money) that you can rehab and place a tenant, then refinance, allowing you to recover all the money back, and repeat.

So I would supplement my income by flipping cars.

My real estate investments are a supplement.

Do you really like them that much that you are willing to supplement their rent?

I've done this and plan to do more to supplement my retirement.  

I stumbled into real estate investing while looking into ways to make passive income to supplement my regular job. 

This means you cannot use the money in your own interest, so these accounts will likely be a good supplement to investing you do outside of retirement funds, not a replacement for it.