HI Abigail,Acquiring a loan, lenders always look into 3 metrics Income/Assets/Credit.

They'll want all the normal stuff; bank account info, LES for several months, hard credit check, etc.

Lending is tough, you need to know the market you're lending in, usually you want to have an understanding of credit-risk and be able to pull credit and run background to get a better read on your borrower.

Just ensure you keep track of when the property use changes.

To qualify for debt, lenders generally look at net worth (aim for the loan amount), liquidity (10% post-close), experience, and a solid credit score (ideally 680+).

I use Stessa only for the tracking feature (transactions).

I bank with Navy Federal Credit Union, and they have a great 20 year interest only HELOC option in which I could utilize my substantial home equity.

CA taxes residents on worldwide income but may provide a credit for taxes paid to other states.

If you want me to give you a quote, I'd need to know the address, 1st lien details (type of loan, balance, interest rate), credit score, income/DTI details, and target LTV (can go up to 80% CLTV on the 4plex). 

As a generic advice:  I would recommend paying off any credit card debt, or high loans.