Also, your investment is usually secured by the underlying property and a personal guarantee. 

We've been trying to get the final tally so we can file a judgement and have the security deposit transferred to us.  

@Edward Oliver if you currently own the property you should be able to just secure it.  

Buying with cash is the safer more secure route but if your goal is to eventually become a full time investor you cannot scale the business using just cash.

Correct me if this is wrong, but securing the property with 100% financing is just to ensure the seller doesn't sell to someone else or get cold feet while the wholesaler finds a buyer?

Unlike passive rental income, the income from an active trade or business is subject to self employment tax (a nasty 15% tax commonly referred to a "social security and medicare" by working folks).

Does this mean the only way to safely buy at these auctions is to secure redemption rights prior to the auction, by contacting the current owner and negotiating a deal?

This type of investment offers relatively secure, high returns that make the fees of self-directed accounts worthwhile for me.  

While my full time profession is in the securities brokerage industry, I have been working on the side as an amateur RE investor. 

I have an offer out on one in Crowfield Plantation and I'm hoping to secure it.