@Mannny Lubana
1. If the property is negative CF, see what potential there is (ie: can you charge for parking, laundry, storage, is the rent too low, can you reno and increase rents, etc). Keep in mind, you want to buy at the value it is at now, not what the potential is. Just because other people buy doesn't mean it is a good deal. If you are looking at MF, you will need 20%+ d/p. Depending on the appraisal, the lender may require higher.
2. It is not just about CF/door. You have to look at the mortgage paydown, expense ratio, debt servicing, market, your client profile, reserve, etc. If the building is going to require some major repairs in 5 years, then your $100/d will be eaten up very fast.
3. Some people don't buy for CF. Sometimes, they put in offers to get it under contract and then negotiate the price down after their due diligence. They may have another use for the property that you are not seeing. ie, I recently got into a 3 unit property where we knew we could convert it into 6 units. Some people buy at 'potential' value.
I am assuming you are having a 2nd set of eyes on your analysis. Also not putting in too much buffer in your analysis. Good luck.