I think the family-purchase/gift-of-equity direction people are pointing you toward is probably the cleanest starting point, but I would approach this as a title-and-capital-structure problem first and a loan-product problem second.
You have roughly $270,000 of apparent equity between a $350,000 value and an $80,000 payoff. That is a very strong position. The danger would be taking that unusually strong equity position and solving an $80,000 title/payoff problem with expensive short-term debt simply because it is easier to close.
My first move would be to put a Florida real-estate attorney or experienced title company and a renovation lender into the same conversation. I’d want them to map the transaction from beginning to end: your father conveys title, the private lender receives its exact payoff, the lien gets properly released, any gift of equity is documented at closing, and the renovation money is available under a financing structure you can actually afford long term. I’d much rather solve all of that in one coordinated closing than transfer title first, borrow somewhere else second, repair the house third, and hope a refinance works fourth.
Before choosing between HomeStyle and 203(k), I’d get real contractor bids for the structural/exterior work and the pool. “Needs structural repair” can mean $15,000 or $150,000, and until you know which one you have, you don’t really know what financing problem you’re solving. I’d also want an insurance agent involved early, because property condition can affect whether the house is insurable in its current state and therefore which loan structures are actually usable.
The 203(k) option is more interesting here than it might initially appear. HUD currently allows repair of an existing in-ground swimming pool under 203(k), and structural repairs are squarely within the program. Whether you fit the
Limited or Standard version will depend on the scope, complexity, timeline, and documentation required. (HUD)
HomeStyle can also combine a principal-residence purchase with renovation financing, and Fannie Mae permits a gift of equity from an acceptable family donor toward down payment and closing costs. One nuance I would not miss: a gift of equity cannot substitute for required financial reserves. With structural work involved, I would want meaningful cash left after closing rather than engineering the transaction so perfectly that you own a $350,000 house and have $700 in the bank. (Fannie Mae Selling Guide)
That's also why I would put the "HELOC immediately after closing" idea behind the renovation-loan analysis rather than automatically making it Plan A. A HELOC may ultimately be useful, but you would be betting that the post-transfer property condition, appraisal, insurance, your qualification, and the HELOC lender's guidelines all cooperate. If the structural problem is substantial, I'd rather have the repair capital committed as part of the acquisition than discover after title transfers that the next lender doesn't like the collateral.
Hard money would be much farther down my list. I’d use short-term money here only if there were a specific problem conventional renovation financing could not solve and I already knew exactly what permanent financing would replace it. “We’ll refinance after the repairs” sounds simple until rates move, appraisal comes in low, seasoning becomes an issue, underwriting changes, or the project costs more than expected.
I’d also have somebody model the family side before setting the purchase price or gift amount. Your father having a lot of equity does not mean the transfer is administratively or tax-free. Florida imposes documentary stamp tax on real-property transfers based on consideration, including certain debt involved in the transfer, and there may also be federal gift/basis consequences depending on how the sale and equity gift are structured. That doesn’t make the transaction unattractive. It just means the deed price, gift amount, payoff, and repair financing should be designed together rather than independently. (Florida Department of Revenue)
If I were sitting in your chair, my sequence would be: verify title and the exact private-lender payoff, get structural and pool bids, determine the as-is and likely as-completed value, run both HomeStyle and 203(k) with lenders who actually close those products, have the attorney/CPA model the family transfer, and then compare the resulting permanent monthly payments.
You have a very favorable starting position because the problem is not lack of equity. You have plenty of equity.
The job is to convert that equity into clean ownership, a repaired house, and sustainable long-term debt without letting the financing structure consume the advantage you already have.