Then, you add on the extra buying pressure the market is seeing from the new tax laws regarding bonus depreciation and that opportunity zones should have its guidelines finalized "soon" and we may see sustained buying pressure in the market. 

No money down deals depend on you over paying for a property or overleveraging yourself in a hopefully short gamble.

@Sky LinThere are guidelines as to the % of owner occupants in a condominium complex that must be met for a originator to be able to sell the loan in the secondary market.

2/ Will I need to follow any special guidelines to be able to show the IRS that the money that I used for the investment property purchase really is the money from HELOC?

IF you do not then save until you do.What I write about is perhaps a less known approach where everyone has been used to just doing a cash out refi or adding a HELOC to their personal residence for quick cash and taking their chances to be successful while adding more debt to their personal residence that should be protected and not gambled on.

@Chris Mason  could give you a definitive on this one Lenders can in fact give credit for the extra rent being counted as down payment, and here's the guideline from fanniemae.com direct. 

The appraisal can not be used for the financing unless it follows a real rigid HVACC appraisal guide line that  must be managed by the bank.

@John Williams I will say this - the safest and best way to protect yourself is through abiding by SEC regulations and guidelines.

@John Williams insurance and warranties always favor the "house" just like gambling.

I work too hard for my money to gamble it and I’ve seen proof of concept play out with my real estate rentals .