Best financing for home renovation

[Matthew Fermino]

I am building an Inlaw apartment for my mother and trying to determine what the best way to finance this would be. i'm fairly certain I will just try to find the best rate for a HELOC but I always get great advice I wouldn't have thought of from the BiggerPockets community here's my situation

I have two properties today.

My primary residence where the in-law will be built that I just refinanced down to 2.75%. I owe 680K and it is worth about 950K.

I also have a vacation rental that I Airbnb. It is worth about 680k and I owe 500k.

The Inlaw addition will be about 150K. I’ve already checked and have approvals with the town I just need to figure out the financing.

I'm thinking a heloc that will let me take 85-90% LTV.

Thanks in advance for any additional Or creative thoughts