Today I called the head of the Urban Renewal Agency agency in Oregon City to ask him about sewer hookups vs. septic tanks. I was pretty impressed that he was so easy to get ahold of (I got him on the second ring). He was able to answer my questions, and point me in the direction of some other contractors to hire. It essentially worked out to a $2500 "connection fee" just to get on the sewer, as well as the cost of decomissioning the old septic tank. Unfortunately there is a grandfather clause that says if you're in Oregon City and on a septic tank that you can keep it until it dies, you're just not allowed to put a new one in. So that doesn't help me negotiate this house any. I did call my realtor and tell him to offer another $2k which would cover half of the $4k that he said it would cost to move to the sewer. I doubt he'll take it, but at least I offered.
I imagine I'll probably be out looking at more houses this weekend. Kinda sucks, I was getting excited about being finished shopping around. Guess not.