Duplex to Quadplex? Construction Loan Questions

[Ian Jimeno]

Hey y'all,

I currently own a duplex in Normal Heights, San Diego area. I just did a feasibility study on the property and can build a total of 3 ADUs along with the single family home on it. 

I'm confused on how the financing and construction loan would work. Right now with the feasibility study We're anticipating about $4,000 for the SFH and $2,200/mo/unit on the ADUs, totaling about $10,600/mo in rent revenue so the initial rents look great.

However, I don't know how the loan will play out. Currently my mortgage is $4,600/mo and the total rent is $5,600/mo

I just need to know how it all works and if it's even worth my time. I know it'll significantly increase the value of the property by making 4 total units on the lot, but refinancing out of my 3.75% interest rate seems like a huge bummer.

Thanks in advance!