I'm brand new to buying homes. I'm in the Chattanooga, TN market btw. Here's what I've seen more than once. A house that rents for $850 plus a mobile home that rents for $500. The market value of the house and land to a prospective homeowner is about $70k. The market value of the mobile home is about $15,000. But because the seller has $1350 in income, he wants $125,000 for everything. He bought it 2 years ago and has about $80k invested. Can't get myself to even offer him $100k. Am I not thinking clearly here? Thoughts are appreciated. 

Don’t overpay just because the seller wants to get a premium. You already know the market value is $85k give or take for both properties. Your offer should be less than that as you are an investor and not in the business of paying full market value unless you love the deal and it still pencils out but no matter what you should stick to your numbers not his.

It is always best to start with what is right for you and make the deal fit in your guidelines and rules rather then figure out what the seller wants. If the deal doesn't fit your rules then it doesn't work. Move on. Win win is always a great idea but this doesn't sound like a win for you unless you get some awesome creative terms.

It shouldn't matter what the seller has invested in a particular project.  The math works or it doesn't.  I wouldn't want to own a mobile home because they are not the easiest to sell, especially if it's on the same parcel as the house.  I own a PM company here in town and we manage all kinds of assets all over town and N GA.  The one certainty I can tell you is that all my clients evaluate purchases in their own way.  If you're not comfortable moving forward then you have your answer, but what doesn't make sense (or does) to you might make sense to someone else.