I'm thinking about using a HELOC to acquire the property and then refinance to pay back the balance.

Using a 1031 exchange to capitalize on better opportunities is a great strategy.Your point about avoiding over-leverage is particularly eye-opening—it's a reminder of how critical it is to balance leverage carefully.

The goals you have and why you’re investing will keep you focused on the best strategy for you to build a balanced portfolio. 

Sellers need to be mindful of the time value of money, using realistic interest rates and structuring the deal to protect their position, whether through securing a first-position lien or obtaining a personal guarantee from the buyer.In the end, seller financing can be a win-win, but it requires a balance.

Some lenders allow you to go up to 90% combined loan to value meaning whatever your balance on your first mortgage is plus the equity loan can go up to 90% of your homes value.

Buy & hold investors may consider lower cost areas like Aurora, Joliet, SW Chicago, and others to get a balance of cash flow while still investing in a decent area.

What do you suggest is the best entity classification to choose from for a new, up-in-coming business owner to get the best balance between liability protection and tax advantages? 

As a fellow professional looking to get into real estate investing, I can definitely relate to the challenges of balancing your practice with exploring investment opportunities.

I balanced cost vs. forced appreciation which ended up making that property a better BRRRR with most of my cash coming out during the refi.

Is it true that this would make it harder for me to get a loan from a bank for the remaining balance?