If you want to learn to ski, the best approach is to start off with the simplest strategies on the easiest terrain, and then gradually build up to more advanced strategies and terrains as you gain experience.As others have mentioned, syndication is an advanced strategy that is not well-suited to beginners. 

One of these is Loan Purpose.Generally there are three buckets for "Loan Purpose" in DSCR Loans 1) Acquisition 2) Rate-Term Refinance 3) Cash-Out RefinanceAcquisitions are the simplest.

The simplest way is to send a check every time you get an invoice.

Now there can be variations of this and some hybrid structures but those are the simplest and most common ways

Look, I can site a multitude of data based reasons for this but let's take the simplest of them all, inflation.

The simplest way is  to have the private lender loan you the money.

After that in a few years I sold both and traded up to an apartment complex. 100% Repetitive house hacking is one of the most efficient, simplest ways to build wealth.Folks often lament that "it takes work to move every year" ...true...But, y'know what takes a LOT more work?    

Rinse & repeat until you hit the limit of 10 mortgages.It's arguably the simplest way to acquire more properties with the best debt terms available.Since you already have 3 properties, you presumably already have a lot of the necessary experience to execute this strategy (e.g.; market & property analysis experience, due diligence experience, property management experience, etc.).And, since you also have good W2 income, if you want to mix in some other strategies (e.g.; and occasional BRRR, etc.), you can probably do that...though, I suggest that the aforementioned strategy should be your bread and butter (since it's lower risk and less work than ARV-dependent and more complicated strategies like BRRR'ing).As for whether to pay off the debts on your existing properties...this depends on factors like: what are your current debt terms?

That would give you a portion of duplex for yourself (though there would be a mortgage)Or.. the simplest was proposed above, sell it, split the proceeds and use yours to invest in another property.

We are well on way into a REI industry where entry is difficult, expensive, exceptionally detailed, where small variations of #'s or %'s can mean success or failure, where a person with limited means is not afforded a seat at the table, and the industry is dominated by highly professional, well funded, organized operators, or in simplest form, a normal investing market.