I agree with @Eric Thomson about factoring in maintenance and vacancy cost. I would be a little more conservative and factor in a little more for 2 reasons; first this is your first investment and you will be on a learning curve, secondly it looks like the second floor has not been updated so you will have to either update it yourself for will have to start repairing things soon.
I have few other questions here. Why is the seller selling (sounds motivated)? You can definitely negotiate the price down or for favorable terms. Do you have the reserves to put down? Are you managing it yourself or are you going to have a company step in? Do you have experience in construction or do you need to contract out all the repairs? Is it rented out and how long is left on the contracts? How much will you be receiving in security deposits from the owner? I could go on with the questions but my point is that you need to open up the lines of communication with the seller. If the seller is distressed you could be sitting on a gold mind after negotiations or the seller could be looking for a sucker to take over their problem. If they have a problem it is a good thing (that is what we look for), as investors we are problem solvers as long as the terms are good.
