Part investment and primary question in regards to a lender

[Ruth Schrader-Grace]

I'll try to be short here. The scenario is moving from one area of Florida to another. Will sell primary to buy another primary but as life goes one will not sell at the same as I want to buy nor do I want to be rushed. Also own a secondary with thoughts of perhaps selling it as well. If I find what I want before the current primary sells it would seem the only option is to do a HELOC as I intend to repay it within a year or less. I would think a conventional "temp" loan would be foolish cost wise with closing costs as they will be and interest rates or maybe interest rates would be better. Not sure.

If I do the HELOC I could essentially pay cash for either the new primary or most of it or pay cash for another secondary and basically swap out secondary's in essence and wait to find the perfect primary. Intention is to later rent out the new found secondary after getting the new primary.

My question is two fold here. One is the scenario I propose a good idea both financially and tax wise if anyone knows. The other is what is the best way to do this financing with the least amount of output cost on closings, etc... Of course I could just sit and wait for the current to sell and then pay cash for my new primary. But....one of us has to go ahead of the other for work until the house sells and hopes are to not be apart for too many months with this transition and properties in play. With said scenario rent falls into the equation if no purchase is made soon which to me is literally throwing money away or giving it to someone else basically bleeding money with zero ROI later on.

Thoughts? Advise? Please let me know if I have not explained this clearly. There is so much math involved and I have myself doubting all the scenarios to see which is clearly the best way. Being both investor and primary buyer and seller is daunting today so I decided to reach out to see what opinions or thoughts are here. 

Thank you in advance for your responses!