Ok there are a lot of confusing answers here that don't really apply to the original question.
It doesn't matter what property secures a loan, it only matters how the loan money is used. See the loan tracing rules explained in IRS publication 535 in the Allocation of Interest chapter. If you have a HELOC, cash-out refi, etc. from your home or any property, you can use that money to buy/improve a rental property, and then the interest from that loan is deductible as an interest expense on the Schedule E for your rental property.
The answers that talk about interest deductions for your home on Schedule A, Tax Cuts and Jobs Act, Pub 936 qualified home interest, etc. aren't applicable to the original question (but they might be answers to other questions people asked later in these posts).
