You would need to speak with a mortgage broker who understands rental properties of this type. I do know that lenders today need the building to be positive cash flow. You would need to put enough money down to make the payment less than the rental income for all four units.
You can only estimate the sale price you will be pre-approved for when it comes to units considering each 4 unit building will have different actual or market rents. For the most part you should have a range so before viewing or making an offer on units the numbers need to be run on that particular property.
Any further financing questions contact me directly.