We have established relationships with them and they trust us when we bring a deal to them or when we advise them on the next course of action with their current investments.Couple things I would say to you on this strategy. 1.

That property is in a different group.Next, establish what the current cost to buy is based on properties within that group that are For Sale the day you are doing the analysis. 

Is a HELOC on an investment property something that would still be considered a personal loan or would I need to venture into establishing a commercial line of credit on the properties?

I would recommend establishing a strategy that is not fully dependent on market timing. 

Each designated LLC has its own governing documents establishing its members, managers, and membership interests.

Versus my mortgage loan officer or Edward Jones advisor haha. 

We found it working with our Envision Advisors Agent Leah Keeling.

I know hiring a CPA or advisor is a good idea at any point, but at what point in an investor's progression does it become a necessity?

I work with agents because of their expertise in their markets, and yes a little help in analysis but you must establishes your habitat as an investor. 

If you want to be in it for the long haul, start establishing those relationships now so you create repeat business and a strong referral network.