Sounds like you're trying to extract max equity? 

And the banker told me if I join Chase private client, they can do a cash-out refin on my current house and extract $290K out of it, so I can pay the investment house all cash, and they can do 3.75 for a 10/1 ARM loan.Should I do it?

I have been involved in residential mold extraction for nothing other than pure lack of HVAC use.

They'll want a copy of the plat for your lot as well as the footprint dimensions of the house to be moved (the former, presumably you already have a copy of, the latter may need to be physically measured or extracted from the plat of record for it).The physical move of the existing structure is just one scope of work among many.  

You can use cash-out refinances to extract more equity forever.

Ideally, I achieve infinite ROI via the BRRRR but I do not achieve a full extract of my investment unless I get a significant assist via appreciation (so I fail on the infinite short term ROI). 

Goal is to extract equity from this project ASAP for another. 

Extract your capital and do a 1031 exchange into a MFR that can generate better returns.Some notes about your analysis:Since you already own the property you'll be able to refi pretty quickly, but in a typical BRRRR you should expect at least a 6-month seasoning period before a lender will refi based on a new appraisal.You're missing the following expenses:CapEx, should be around 15% when combined w/ RepairsManagement (10%) always include this even if you plan to self-manage at firstVacancy (8%)These additional expenses make you cash flow negative, even at 60% LTV, which is why I recommend selling this property.

Rates are low and you have solid equity to extract so now would be a good time.  

Really, I'm looking for a way to extract and build upon the equity I already have in real estate.