Off Market San Francisco Duplex Help

[Jaime Rossini]

I found an off market duplex that I want to buy as a house hack. It's more than I can finance and I have a private party that may be willing to do a personal loan to fill my gap in financing. My issue is that I don't know how to run the numbers to figure out how or when/if I will be able to pay the private party back. I tried to use the buy/hold calculator on BP, but it doesn't really take everything into account and I am not a spreadsheet builder. 

The property is in a great area on a corner lot with 4 parking spots and I would love to hold and rent both units when I eventually move out. I just don't know that I would ever be able to pull out the amount needed to pay back the private party in a re-fi . I've been trying to analyze different exit strategies. There is a tenant in one unit (not protected) and a vacant unit. The units are in decent shape, but could certainly use upgrading. We have friends who might be interested in partnering as TIC and condo converting, but (and I know condo prices are low right now) from my research it doesn't seem like that's all that profitable. It's zoned for 3 units and there is space to convert a free standing garage into another unit (but is that more desirable than a duplex with rent control laws?). I know it is a unique property and the location can't be beat...I just can't figure out how to make it work. If anyone experienced in San Francisco has any insight to offer, I'd be grateful.