weirdo househack: fourplex with a partner / unequal shares - how?

[Mimi H.]

I may have an opportunity to purchase a fourplex with a partner (non-romantic). What we'd like to do is the following:

I make this a point because he will occupy one of the units and I will occupy the other. He's not interested in "running" a rental and wants to pay for his portion in cash, which helps from a mortgage perspective. I'd be the primary on the mortgage and own the rentals. Does anyone have any experience with this and can offer advice? aka, gotchas, etc?

Thanks!