Since the original loan remains in the seller’s name, you may need a nominee interest allocation to deduct mortgage interest, as the Form 1098 will likely be issued to the seller.

Since the HELOC was used for a business use (renovating the rental) you can deduct the loan interest against that rental using the interest tracing rules found in §1.163-10T. 

Bought from neighbor next door to rental we owned.

As I approach the end of my current lease, I'm eager to embark on a journey of house hacking with multifamily properties.

The "big" firms like AA may get a lot of hype but they generally can't compete on the next level tax strategies (Family office type strategies) nor customer service as their employee turnover is quite high.  

If they fail to pay the new full amount send a pay or quit for the missing amount with late fees.

And you have taken the extra 150 hours required for the broker's license? 

How do you approach educating people on the realities of the business? 

You might also meet title agents who have resources on, say, foreclosures or probates…and might recommend lenders who actually lend on more difficult projects (as the title companies also know which lenders can close and which are difficult).I also go visit open houses to see what sorts of finish to put on my renovations or to look for the next house or area in which to purchase.  

Just a few tips to look into but it usually takes some time to gain steam on your first listing so be patient and keep analyzing the local compeition /your own listing.