Is there a standard method for knowing what kind of offer to make on multifamily?

[Russ Mooneyhan]

I have been looking at apartment complexes. I managed to get 1 8 unit and 1 6 unit building over the last few months and have done well with them. The cash flow jump was substantial and so of course I'd like to acquire more. To a degree I lucked into the 2 buildings so my biggest question is the title. I'm sure there are lots of variables so its not a one size fits all answer normally. However I am wondering if investors in multifamily go into it with asking for 10-15% off of listing price? Or is there some other method that works better. I cannot pay cash for the building. I would be looking at properties at 1 million or less. Any advice or a point in the right direction would be greatly appreciated.