I really don't like this approach at all, and I think that folks who use HELOC after HELOC to finance property will find that real estate compounds financial pressure on their lives, rather than compounding freedom.
Here's an example. Suppose that I purchase a property or $480,000 and after a $360,000 mortgage, I generate $6,000 per year in cash flow (5% CoC ROI with $120,000 down payment).
This makes sense and for some investors, would be considered a "single" or "base hit".
Now, let's assume that instead of bringing cash, I brought the $120,000 down with a HELOC from my primary residence, at an interest rate of 6%.
The interest alone on this HELOC is $7,200. So, right off the bat, I have to bring $1200 per year to continue operating and owning this property.
But, we also, at some point, have to pay off the HELOC. A HELOC is a short-term debt instrument. Even if we assume we will pay off this $120K over 5 years, that's $2,000 per month in principal repayment. $24,000 per year.
Rather than putting money in your pocket, this HELOC financed rental property is requiring you to hustle harder than ever to come up with $25,000 per year to keep your rental, for FIVE YEARS.
While it is possible that at the end of 5 years, you could have a cash flowing asset, that has appreciated in value and amortized the mortgage, those are not likely to be a fun five years, and for me, defeat the purpose of real estate investing in snowballing my wealth and making my life easier and easier, financially, with each investment.
The HELOC, in my opinion, is much more appropriately used as a short-term financing tool. For example, I might use it to fund or supplementally fund a fix and flip project, or a BRRRR investment. For this purpose, it can be a great alternative to private or hard money.
I just sometimes worry that folks who try to get into real estate, and use HELOCs to fund down payments on long-term investments, will find themselves in for a very hard road ahead, especially if the markets do not appreciate the way they did the last several years.