With big ticket items staring down on you ...

I've heard of the book by Michael Blank Financial freedom with real estate investing, but looking at the reviews it seems to talk more about syndications.

If you’re still coming up blank, reach out to me and I can give you my top picks (I have no financial lender/broker affiliations).

We are staring out with a HELOC on an investment property. 

I have listened to many podcasts from Michael Blank (among others) about investing with no or low money down.

Mentioned, proof of funds is used to show that you have all the funds needed to do an all cash deal.Could be either bank statements with account numbers blanked out or a letter from a bank branch person stating you have the necessary funds in your account.If you are getting financing for your deals, then you need a pre approval letter stating you have the budget for the deal.Theses are usually required when submitting offers.

For bigger properties Michael Blank's Deal Analyzer is a good one

The most widely used one I see is the one from Michael Blank.

Most states even have preformatted contract addendums for seller financing, so your agent would just full in the blanks with the broad strokes of your offer. 

A monkey can file an LLC and fill in the blanks, that is something you could save money on, then using the attorney for the heavy lifting.