Hi John-
Great question and congratulations on getting closer to purchasing your first investment property.
To answer your question, it is always preferable to use other people's money which includes the bank. This gives you a greater or infinite return as you essentially create money from other people's money. This is a skill to practice and build up your tolerance for doing.
That being said, whatever you use the money for has to cash flow and pay back the borrowed money for you.
I don't think the HELOC you arranged is necessary bad. It forces you to pay on the principal while the money is being used. It is very common for investors to use a HELOC to get started investing in properties. Another option is to see if they will convert the balance used to a Home Equity Loan instead of a Home Equity Line of Credit to fix the interest rate but your current HELOC may be just fine.
Anyway, you want to find a property that needs a little work so that when you buy it and fix it to rent you can refinance the equity back out that you put into it as much as possible so you can keep your money moving to the next property. Also, ideally, the property will have strong cashflow after using a property manager to help manage the property. This is still possible in areas of the Midwest like Michigan where I am from.
Some lenders will give you a HELOC on the equity in an investment property or you can do a cash out refinance to get your money out. There are pros and cons to both. If you have a low interest rate on the purchase of the property you may want to use a HELOC to get the equity out to keep the low fixed mortgage rate on the primary loan. If the difference between the rate on your cash out refinance and exiting long term mortgage is similar than a cash out refinance makes sense.
You will want to establish lender relationships for the purchase and refinance before buying explaining what you are trying to do and understanding the lending terms available. This is the BRRRR Method of investing for your reference.
As far as paying down the original HELOC on your primary house you can use the cash flow from the property you invest in. This is the best way to do it and if you need to, down the road, you can always pull additional equity out of your investment property to pay off the HELOC on your primary house if you need or want to.
Bottom line, you will need to get comfortable managing other people's money, including the banks, well and using other people's money investing in real estate.
One last word of advice, make sure you have plenty of reserve in your cash on hand or equity funds for each property for the unforeseen repair. You will sleep better at night and something always comes up. Maybe some of your monthly play money could become your investment property emergency fund.
I guess one more. :) Think about getting your HELOCs from credit unions as they are less likely to freeze or cut your line of credit if the economy gets shaky. No guarantee it won't happen but less likely with credit unions.
To your success!