1st I'm not an attorney, so I can't give advice, but if I was you, I would form my LLC in Nevada or Wyoming, I would want to form my LLC in a state where there is not tax on the LLC. You can register any State's LLC in any other state with a foreign Entity Registration with the state you want to do business in.
If you get a HELOC on your personal residence couldn't you claim the interest on against your personal income taxes?
Also, for purchasing your rental property you can get 80% financing very easily with no Tax Returns via a DSCR loan, depending on your credit, and Down payment, you could see rates from 5.99-8.99%. Personally, I really like the BRRR (Buy, Fix, Rent, Refinance Repeat) model, which is to buy a property fix it up, rent it out and refinance it and do another one. This accomplishes 2 things, 1 you are gaining instant equity, 20-30% each time you complete the process. 2. Financing for 1-4 units is saturated, and there are hundreds of lenders in that market. Once you get into the 5+ unit properties, the lending market evaporates, there are very few lenders in this market and the rates are 1-1.5 higher than in the 1-4 unit market, if you are thinking bigger, the 10+ unit financing is best case 65% LTV, where the 1-4 unit market is 80% LTV for Stabilized rent ready properties, and if you are buying a fixer upper you can usually get 90% of purchase and 100% of rehab. Hope this helps.