I’m not in favor of a HELOC because inflation should make interest rates rise. If you’re pushing the financial boundaries by not being able to finance these repairs/remodel, then you should refinance either home at today’s low rates. You’ll likely get a lower rate on your residence — but the interest on the money you pull out will not be deductible if used to repair the other home.
The obvious question is: “Why not do a two-part remodel?? Half now, and half when you’ve managed to accumulate most of the rest of the money needed?”