The truth is, there is no ideal investment strategy, but knowing what you want to get out of it, the capital you have available, the time you have available to invest in the research etc. can help you decide which way to go.Keep asking your questions in the forums!

I'm just now starting to do research on other markets to find an ideal place where I can invest.

A four-unit building would be ideal, but I have not found many in the Charlotte area online. 

Currently I’m in search of my first property which I plan to house hack, ideally in the Central Maine area.

You will be able to find your best price and pick your ideal cabinets for your project. 

An ideal that is already proven with track record. 

I would also love to get into multi families, ideally start off with 5-20 units to get my feet wet and get through the learning curve before jumping in any deeper.

I remember my first deal, and I ended up wholesaling it.

If you put stock in CAP rates (I don't) you are looking at below 5%.Additionally, you would require a larger downpayment to bring your Break-Even-Ratio (BER) below 85% and your debt coverage ratio (DCR) over 1.25 (in my experience, commercial lenders like to see 1.4 or better).While market rent may be greater, remember you are paying for the current performance of the business, not it's potential -  which will require further work and capital from you to achieve.  

As you mentioned, I like the HELOC because of the flexibility, which makes it ideal for BRRRR and rehabs where you can cycle the money over an over and it costs you nothing when you aren't using it.