I refinanced mine out of FHA into conventional prior to doing a HELOC so that i would have FHA available if i wanted to use it again.

It depends on if the loan is FHA, VA, USDA or conventional and if the guy you are buying from went through escrow or just did a "kitchen table closing", if the property was in foreclosure or late on payments in the last 6 years (right, you're in Washington State - where socialism went when it died in the Soviet Union) (I'm from Seattle, by the way ;-), how the underlying loan payments are being made, the status of the person on the underlying note, you have to determine who is going to pay the excise tax on the transfer and of course you need to see the terms on the Lease to Own, etc.But, yes, it should be able to be done.

Conventional loans under 10% down would also be capped to 3% concession while higher down payment conventional will be more (6% cap at 10-25% down, 9% at 25%+ down). 

Conventional Mortgage loan for property that I will live in (large loan)3.

I've found a building (for my business), which the seller own outright, and conventional financing is not an option.

I’m trying to figure out if I can cash out refinance to an 80% LTV conventional loan on this type of property or should I refinance down to what the remaining balance is and then do a HELOC to pull out the rest of the equity(I’m not sure if that’s even an option).

The conventional home owner type lenders at the same place won't have much of a clue usually.

@Dean Klein The product I am thinking of is a conventional loan with 5% down.

It's scheduled to close on 1/28/2020, and we are using a second-home conventional loan because we do not qualify for primary (we're employed in CA and will not be in the home within 60 days of closing, more like 100) and we don't have the capital to put down on an investment loan (we want that extra cash we have saved for the BRRRR, AND need proof of 6 months of payment saved up anyways). 

For my first property i went conventional 97% financed and 2 first time home buyer "grants" ended up only paying $1200 total at closing.