Need advise for possible purchase of a four unit rental investment

[Jack Srimani]

Hi,
I am looking into a investment property for rental purpose. This is a four unit property. Three units are occupied. The fourth unit is not as this side of the building has a roof leak. The roof is twenty five years old. In order to get the forth unit rented a part of the roof needs to be fixed. This will cost about six thousand dollars. Also carpet needs to be replaced and the unit needs to be painted. The asking price is 90000. However the seller is motivated and is open to negotiation. Renters pay their own utility. Now currently the rents are 550, 550 and 450. The unoccupied unit can fetch 550. The building is 110 years old. Now I do not want to buy this and spend nearly eight grands from my pocket to get rents from the forth unit. Also I am very much aware that in four to five years other side of the roof need replacement which is probably another six to eight thousand dollars. I would like to buy such that the nine thousand dollars needed for renovation of the fourth unit will be incorporated in the purchase price. Is there any way to do that. I appreciate the feedback.
Thanks.
PS: Also what should be the maximum price you would settle for this kind of investment.