The rule of thumb in commercial investing is that the property must be 85% occupied and be at least a 10% capitalization rate in order to qualify for bank financing. Since only 2 out of 6 units are occupied, this means you are only sitting at 34% occupancy, which makes this a distressed property in commercial terms.
If you email me, I will send you a cash flow evaluator to analyze a performa you will have to construct. Based on the performa (what the future income / expense will be) you will base your top appraised value.
The formula you will need to use for your offer is:
1) Top appraised value (minus) repairs needed, divided by 2
That formula will be 50% of the AS-IS value.
This is assuming you are using:
A) Hard Money
B) Private Money
Since the seller is distressed, and cannot sell this property to ANYONE but a cash buyer, I would suggest you come up with some owner financing senarios. For instance, if you have the cash and know how to fix the property up, ask the owner to finance you with zero money down.
You can also do a master lease option, where essentially you are leasing the entire 6 unit from the owner with an option to buy it later down the line. You agree to pay the owner more in the future for giving you an option to buy. And you can negotiate in the contract to ask the owner for a construction budget.
Those are just a few ideas. But, once again, this property WILL NOT qualify for traditional commercial financing. This is considered a high risk loan that only a hard money lender or private lender will make.