Financing Options after constructing 4 ADUs

[Andy Chen]

Hi all, need your suggestions. 

I am planning to build 4 ADUs on my triplex. My primary mortgage rate is excellent and I definitely don't want to lose it.

Any suggestions to cash out refinance at fixed rate without losing the primary mortgage after construction?

I have looked into HELOC or HE loan, the max is only $500k. The added value (market value) from the ADUs would be around $1.5~2M and the total cost for the project is around 700K.

Note: After construction, it will be 7 units and it could fall under commercial loan.

I am hoping to do a 2nd loan to pay off the construction cost and cash out without losing the primary loan.

Any suggestions? Thanks in advance.