A follow-up to my own post and I will try to address the issues other people raised:
The City's "full market value" I referred to- I don't know what entity determines this number, I assumed it is determined by the City, not the County, because it was on the City's website. I was told by the current owner's that this value has increased since they finished their renovations. My impression of the owner's is that they are trustworthy and honest.
To my knowledge, all renovations were properly permitted and inspected by the City Code Officer- they mentioned him by name without me asking, and I happened to recognize his name because I've dealt with him in the past. The wildcard here is that much of the labor was done by the owners, their family, and their friends and members of their church, some of whom are professionals. I was impressed with the quality and scope of the work, but I'm not experienced enough to judge the value of this work, especially since the labor was more or less free. The materials they chose while not top of the line were also not low-budget products since they have been living here for the past 4 years. Key item for me is that both units are in move-in condition as I don't have the time or experience to renovate, so I'm willing to pay a premium for that (this property will be owner-occupied by necessity, I am negotiating to buy another property at the same time).
The exterior issues are mainly cosmetic and repairs can be put off until next year, but there is some rot on the wood porch.
I understand that an appraiser is not an inspector and vice-versa.
I paid to have an appraiser give me a report on the property. I'm not particularly concerned about the expense, and I will definitely make the contract stipulate that it will require an inspection. The appraiser's report came back at $135K, which surprised me. I am going to see if I can track down some comp pricing. I am meeting with the owners later this week, but I still have to figure out what I think I can reasonably offer them.
I think the asking price is fair for the area, the lot, and the condition of the house, and my net cost when the upstairs is rented will be around $250/month after PITI, I actually save money since my current rent is more than that, plus I get all the tax incentives of owning. I was just looking to see if I can save a few grand with a lower offer, and what other people's thoughts were.
Thanks