She can use that money to get a hotel room or short term rental....or stay with family or friends.

The six month cd isn’t the point my understanding is that I can’t just take out the HELOC, I need to actually use the money for my plan to work and a short term CD seemed safe and reasonable 

I will be getting rid of her shortly.

I was only with them for a short interim due to the distance.

I'd rather keep the sub-3% rate for now and finance other properties conventionally for the short term.

Q2 is most important: If the mortgaage is upside down, it would have to be an approved short sale and that could take a very long time to rectify.

Short term (12 months), low loan to value with borrowers who have strong credit and significant assets.

My plan is to add 2 - 6 shipping container type of small houses and an above ground pool at some point to make at least a section of the property short/mid term rentals.

Bought it as a safe bet thinking it would do roughly $35k annually in short term rents.

That is tight leverage for an investment 2nd position loan.A private investor might be willing to do it, it's not going to be cheap at all & will be short-term money & will not be a line of credit to take out at your liking.What is your rate on the 1st?