Again, to reiterate, the risk is less burdened because the property also serves as your primary residence.

If not, you could always maintain 2 separate IRA accounts, one self-directed for private lending, and then another for your traditional investing.

I completely agree with @Ashish Acharya's points about the cost-effectiveness of a HELOC and the potential credit implications if it’s secured by your primary residence.

With the caveat that I'm much more familiar with traditional private equity funds than real estate investment funds, I would caution that the returns waterfall is extremely favorable for the GP.

Currently, I own my primary home and a rental in San Antonio, TX. 

I bought my first two rental houses with a combination of using a HELOC on my primary and using my retirement $.

The primary issue is that building small unit in a single count is some of the most expensive development.In addition, in most jurisdictions the primary unit will become rent controlled (assuming more than 15 years old).  

One of the best hacks if you have limited cash is to buy a primary residence with up to 4 units.  

But if you bought right for yourself, it's immaterial.3) No, this is how most people entering the REI or primary home buying feel right now.

This allows you to access funds while keeping your existing mortgages intact.Second Mortgage: Explore lenders who offer second-position loans on investment properties, though rates will be higher.Cash-Out HELOC : While traditional banks often restrict HELOCs on non-owner-occupied properties, some portfolio or private lenders may offer HELOCs for investors.With $15-20K in liquid funds, look for deals where you can negotiate terms:Seller Financing: Negotiate lower down payments or interest-only periods.Subject-To Financing: Assume the seller’s existing mortgage while covering the down payment.Lease-to-Own: Lock in the purchase price while using rental income to build equity.