Should i buy this multi family?

[Brittany Fife]

There is a four unit for sale and the numbers work out great. The only problem is there is two vacant apartments and my ex husband lives in an occupied apartment and an elderly man wants to move because he’s afraid of the rent being raised. If the old man does stay, that still leaves the owner to get two tenants, get rid of my ex and we would be in a unit as well. Should I put an offer in contingent upon the owner getting 3 out of the 4 units rented? What about if they don’t find someone by closing? It would be such a waste of time. Help!