I believe you will run into complications getting rehab costs covered by trying to arrange as a personal property. Obviously a live in property can create savings on interest rates but lets be honest and consider the fact that it is a business considering the other units. I believe it is better to be listed on good terms with lenders and develop ongoing relationships. Disguising your true intentions can cause unwanted backlash in the future.
Traditionally it should be approached as a business transaction and rehab. The potential exit strategies would be to refinance into a buy and hold property or sell. An interest only bridge loan would be the target. On average expect around 20% down payment but depending on experience can be negotiated down to potentially 10%. Then 100% rehab could be covered.
There is certainly a difference between 4 and 6 units but it is also important to consider comps and the real value of the money injected. There will be more lenders interested at 4 but at the end of the day, if the numbers make sense, you can get someone to bite.
I hope this helps and feel free to message me if you'd like.