How to negotiate in buying two properties

[E Schemanske]

Hello all! I found these two condo units for sale that are in the same complex and I am really interested in buying them. I do not have any experience in investing and I wonder if someone could give me an advice on how I can negotiate the price down. Both units are owned by one seller and it cost 75k/unit. Since I want to buy the 2 units together, what is the reasonable offer for these units? It's located in Metro Detroit and is very accessible to everything. Unit 1 already has an existing tenant. In this market, is it bad to offer 10% below the asking price? In your personal experience, how do you negotiate?