The average buyer has no idea how to conduct a transaction, especially if they move from market to market / state to state.If we move away from a commission payment system, it puts a serious crimp on the agent / client relationship. 

It's a short term product with interest only payments and no pre-pay penalties. 

Be clear and firm on rent payment dates, grace period and late fees.

1) make the payment directly from my HELOC account2) transfer the money from HELOC to business checking account, and then make the payment from my business checking account.

I purchased this 5 Unit building for $140,000, and I used the equity from one of my SFH rentals to come up with the Down Payment!

That's not super thorough or safe for either of you. 5) Use a third party loan servicer to make your monthly payment collections easier as well as the end of year tax documents needed.

The current interest rates 6.9%-7% kill my numbers for an investment property because the mortgage payment already comes out to $1,300 a month with the big 4 included.

If you can manage the payments, it could be a good idea to hold on to it until prices raise and you can sell for a profit.

Without tying up all my cash, what avenues should I pursue to cover the $72,400 cash payment I will need to make the deal happen on top of taking over the current owners loan?

Even with rates where they're at lenders require you to have a certain ratio on the payment of rent vs mortgage.