Use the HELOC on cash-generating opportunities like flips, then use the cash generated to buy long-term buy and hold investments. 

Also started out not too long ago (2023), currently working on my second BRRRR property.

Now he has sold the company and is more of a flat rate charge based loosely on how long it takes him to prepare the return.

REI is a long-term venture; if you cannot hold this will be a very difficult process.  

MTRs fall into the standard long term rental( 30 day +) category and will follow those regulations set for Long term rentals.

And then you could take your time shopping for long term financing once you own the property.

Owning a duplex at 20 is a huge accomplishment, and it’s inspiring to see you’re already planning your next move.From my perspective, real estate investing is a long-term game focused on building equity, paying down debt, and maintaining stability over chasing short-term cash flow.

I have Mutuals and Indexes- I have always played it safe, however, I've waited way too long to invest in Real Estate.

Depending on your current rate or if the current loan is short term or long term.

Honestly with an interest rate like that you could even not pay off your primary and put any excess capital in a high yields savings account and be financially further in the long term.