For practitioners in the real estate industry, the biggest challenge is not just the difficult work, high risks, or immense pressure, but the necessity to learn to let go of complete control over outcomes.

You can probably just go ahead and live in that 5th unit, but I believe whenever you go to refinance it with a bank or what not, the 5th unit will make it require a commercial loan and not residential regardless of what the county records show the property to be. 

The LLC is irrelevant unless you are paying cash or getting a DSCR loan.

I’d appreciate any guidance or tips to get started on the right path.

I cold call and go direct to the seller and I have a 3 person team that pretty much just calls all day long for me.

Here's a https://www.irs.gov/businesses/cost-segregation-audit-technique-guide-chapter-4-principal-elements-of-a-quality-cost-segregation-study-and-report to the IRS website noting specific items that are included in the cost segregation study report. hmm, that website is a 404 error.  

Go with the HELOC.

It sucks for us LLs, because if the tenant is poor, LL won't go to small claims to get award, too, and then there's eventually no record.

Reread what @Stuart Udis wrote.We can testify to the same challenges after 25 years in our marketplace.We also agree with @Kristian Sexton about starting with a PMC.

@Chris Kay go to Meetup groups.